From f8aca6be667851ed9a971c3054bb4d7de304c567 Mon Sep 17 00:00:00 2001 From: Sven Geboers Date: Sun, 31 May 2026 20:00:14 +0200 Subject: [PATCH] docs(blog): Add Overton window analysis blog post 578-line HTML blog post with CSS-only charts, metrics, timeline, and full narrative covering all findings from the analysis. --- reports/overton_window/blog_post.html | 578 ++++++++++++++++++++++++++ 1 file changed, 578 insertions(+) create mode 100644 reports/overton_window/blog_post.html diff --git a/reports/overton_window/blog_post.html b/reports/overton_window/blog_post.html new file mode 100644 index 0000000..a0d1d02 --- /dev/null +++ b/reports/overton_window/blog_post.html @@ -0,0 +1,578 @@ + + + + + +Has the Overton Window Shifted in the Dutch Parliament? + + + + +

Has the Overton Window Shifted in the Dutch Parliament?

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A data-driven analysis of 2,986 right-wing motions (2016–2026) reveals a surprising answer: the window didn't shift. The right-wing moved toward it.

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Analysis based on 2,986 classified right-wing motions, 2,869 two-dimensional extremity scores, MP-level voting records across 33 quarters, and 200 systematically classified policy mechanisms.

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The Question

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After the PVV's historic election victory in November 2023 and the formation of the Schoof cabinet in July 2024, a question dominated Dutch political commentary: has the Overton window shifted to the right? Have centrist parties (VVD, D66, CDA, NSC, ChristenUnie, BBB) become more accepting of right-wing policy positions?

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We analyzed every right-wing motion submitted to the Dutch Tweede Kamer between 2016 and 2026 — 2,986 motions classified by keyword matching and voting patterns, scored on two dimensions (rhetorical extremity and material policy impact), and tracked across 33 quarters of parliamentary activity.

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The answer is more nuanced — and more interesting — than a simple yes or no.

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+The Overton window did not shift right. Right-wing parties moderated toward it. That moderation effect may be temporary. +
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Three Indicators at a Glance

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IndicatorPre-2024Post-2024ChangeVerdict
Centrist support (strict)0.2510.507+0.256Surged
Material impact (2D)2.782.43−0.35Declined
High-impact share (M≥4)23.7%11.3%−12.4 ppDeclined
SVD cultural gap0.2820.428+0.146Diverged
Stylistic extremity1.7181.815+0.097Increased
Temporal trajectory———Electoral jump, reverting
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Centrist support surged. But the motions themselves became less materially impactful — the share of high-impact proposals (M≥4) dropped from 23.7% to 11.3%. The Overton window did not shift rightward. Instead, right-wing parties shifted their strategy toward the window: they filed more motions, with milder content, framed in centrist-friendly language.

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Indicator 1: How Centrists Voted

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The cleanest signal is in how centrist parties voted on right-wing motions. Using a strict centrist definition (VVD, D66, CDA, NSC, BBB, CU), average support rose from 0.251 pre-2024 to 0.507 post-2024 — a Cohen's d of +0.65.

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Not a Coalition Effect

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After the Schoof cabinet formed, PVV entered government, which could mechanically inflate support for its own motions. So we restricted to opposition-only right-wing motions. The effect is larger: d = +0.85, with support jumping from 0.270 to 0.543. Coalition dynamics slightly suppressed the observable shift.

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Centrist Support for Right-Wing Motions (Opposition-Only)
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Pre-2024
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0.270
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Post-2024
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0.543
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Fraction of centrist parties voting 'voor' on opposition right-wing motions. Cohen's d = +0.85.

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The Gradient Persists

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Centrists still differentiate by how radical a motion is — high-extremity motions (buckets 3–5) gained proportionally more support than mild motions (buckets 1–2). This is consistent with genuine tolerance expansion, not a compositional shift toward milder motions.

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Who Drove the Shift?

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The shift is not uniform across centrist parties:

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PartyPre-2024 Migration Voor%Post-2024 Migration Voor%
CDA~18%~40%
ChristenUnie~10%~30%
NSC—~30%
D66~4%~12%
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The two Christian-conservative parties — CDA and ChristenUnie — more than doubled their migration vote share. D66 barely moved. The shift is not "centrists accepting right-wing content" — it is the Christian-conservative wing of the center moved substantially, while the progressive wing barely budged.

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Indicator 2: Spatial Divergence

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If centrists are voting more with right-wing motions, one might expect ideological convergence — centrist parties drifting rightward. Procrustes-aligned SVD analysis shows the opposite.

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−0.30
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Centrist axis-1 drift (leftward, more welfare)
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+0.07
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Right-wing axis-1 drift (barely moved)
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+0.146
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Cultural gap widened
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160°
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Centrist drift direction (southwest: welfare + cosmopolitan)
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Centrist parties moved left on both SVD axes — more welfare-oriented economically, more cosmopolitan culturally. Right-wing parties moved further into the nationalist corner. The cultural distance between the two groups widened from 0.282 to 0.428.

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This is spatial divergence, not convergence. The puzzle: how can centrists vote more with right-wing motions while moving further away from them ideologically?

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+The resolution: Right-wing parties filed a much larger volume of milder motions that centrists supported, while continuing to file high-impact motions centrists opposed. The net effect on SVD was centrist-left divergence: the extreme motions (still opposed) dominated the voting structure, while the surge of milder centrist-supported motions added volume without shifting party positions. +
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Indicator 3: Content Extremity — The 2D Story

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The original single-dimensional extremity score showed no increase post-2024 (d = −0.09). But a single score conflates two independent dimensions:

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These two dimensions are only moderately correlated (r = 0.47). And their trajectories diverge:

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DimensionPre-2024Post-2024Change
Stylistic extremity1.7181.815+0.097
Material impact2.5302.384−0.146
Gap (M−S)0.8130.570−0.243
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Right-wing motions became more restrained in language while simultaneously becoming less materially consequential. This is holistic moderation — both the packaging and the content shifted toward the center.

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2D Extremity Divergence (Wilcoxon p = 0.002)
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Stylistic extremity
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1.718
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1.815
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Material impact
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2.530
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2.384
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Both on 1–5 scale. Pre (lighter) vs Post (darker). Stylistic rose while material fell — dimensions systematically diverge.

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The Gravity Question: Do Meaningful Motions Show the Same Pattern?

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Not all motions are equal. A symbolic declaration ("we express concern about X") is fundamentally different from a bill that restricts asylum seekers' rights. Does the centrist support shift hold when we filter to only substantive, high-impact motions?

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Gravity LevelPre-2024 CSPost-2024 CSΔ
All motions0.2540.509+0.255
M≥3 (substantive policy)0.1920.435+0.243
M≥4 (fundamental rights)0.1140.377+0.263
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The shift is real across ALL gravity levels, including motions that touch fundamental rights. If anything, the effect is slightly larger for high-impact motions (+0.263) than for the full dataset (+0.255). This is not a story about centrists rubber-stamping symbolic gestures — it's a story about genuine accommodation of substantive right-wing policy proposals.

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The Left-Wing Control: Are Centrists Drifting Left or Right?

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A key concern: the SVD shows centrists moving left. Could this mean they're simply voting more with everyone — including left-wing parties — rather than specifically accommodating the right?

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We compared centrist voting on motions submitted by left-wing parties (SP, GroenLinks-PvdA, PvdD, Volt, DENK) versus right-wing parties (PVV, FVD, JA21, SGP):

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Centrist Support by Submitting Party Bloc
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Left-wing motions
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0.498
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0.490
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Right-wing motions
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0.369
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0.531
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Pre-2024 (lighter) vs Post-2024 (darker). Left-wing motions: FLAT. Right-wing motions: SURGE.

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+Left-wing motions: Pre CS=0.498 → Post CS=0.490, Δ=−0.008. Completely flat.
+Right-wing motions: Pre CS=0.369 → Post CS=0.531, Δ=+0.162. Surge. +
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The centrist support surge is entirely concentrated in right-wing motions. Centrist support for left-wing motions didn't change at all. The SVD's leftward drift is not driven by symbolic left-wing cooperation — it's driven by centrists voting more with right-wing parties on right-wing proposals while maintaining their existing voting patterns on everything else.

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Who Filed the Motions? JA21 as the Primary Driver

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Treating right-wing parties as a bloc obscures a critical finding. Breaking down by party:

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PartyCS ShiftVolume ChangeNotable
JA21+0.203+82Only party with volume + support gains
SGP+0.195−91Already mainstream pre-2024
PVV+0.125−185Entered government, filed fewer motions
FVD+0.036−62Remains essentially shunned
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JA21 drives the moderation effect — they are the only party that both significantly increased motion volume and centrist support simultaneously. PVV's +0.125 shift starts from a very low baseline and coincides with entering government (fewer, less radical motions). SGP was already a "mainstream" right-wing party pre-2024. FVD remains firmly marginalized.

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How Did They Do It? Mechanism Classification

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A systematic classification of 200 motions across 10 mechanism types reveals the dominant pathways through which right-wing motions gain centrist support:

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Post-2024 High-Support Motions (CS > 0.5)

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Mechanism Distribution (High Centrist Support, Post-2024)
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Procedural
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32%
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Consensus
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24%
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Restriction
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17.3%
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Institutional
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9.3%
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Other
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13.3%
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The contrast with low-support motions is sharp. Zero system-dismantling proposals (asylum stops, treaty exits, fundamental institutional upheaval) achieved high centrist support post-2024. The truly ideological right-wing agenda does not gain centrist support.

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Consensus framing — appealing to shared values like safety, efficiency, and pragmatism — is significantly more common in high-support motions (24%) than low-support ones (8%): χ² = 6.0, p = 0.014.

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When Did It Happen? The Temporal Trajectory

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Quarterly analysis across 33 quarters (2016-Q2 through 2026-Q1) reveals the exact timing:

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2016–2023
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Stable baseline. Mean centrist support: 0.336 across 25 quarters.
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November 2023
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PVV election victory. The electoral shock.
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2024-Q1
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Structural break. Centrist support jumps from 0.321 → 0.501 (+0.180 in a single quarter). This is 1.9× the average quarterly change.
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July 2024
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Schoof cabinet formed. But the shift began before this — ruling out coalition dynamics as the primary driver.
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2024-Q4
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Peak: 0.648. First full quarter of the Schoof cabinet.
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2025-Q1–Q4
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Steady decline: 0.598 → 0.503 → 0.437 → 0.450.
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2026-Q1
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Reversion: 0.334. Below the 0.4 inflection threshold. Approaching pre-shift levels.
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The trajectory resembles an electoral response function — a rapid jump after the election, a peak during the honeymoon phase, and a gradual decline. The shift may be an electoral-cycle phenomenon rather than a permanent Overton window movement.

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The Voting Margin: A Better Metric Than Pass Rate

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Dutch parliament passes 96%+ of all motions. This makes pass rate a useless metric — it cannot register a shift of any magnitude. We computed a continuous alternative:

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margin = (voor − tegen) / (voor + tegen + afwezig)

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−0.081
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Pre-2024 mean margin
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+0.128
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Post-2024 mean margin
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+0.746
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Q1→Q4 margin gap
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ρ=0.812
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Correlation with centrist support
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Voting margin detects temporal patterns at a granularity pass rate cannot. The pre-2024 margin was negative (right-wing motions lost by 8 points on average). Post-2024, they won by 13 points. The shift from losing to winning is the real signal — not the binary pass/fail.

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Can We Predict Which Motions Succeed?

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A predictive model (logistic regression, AUC-ROC = 0.81) identifies the strongest predictors of centrist support:

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FeatureCoefficientInterpretation
Category: Corona−1.47Corona motions get 77% lower odds of centrist support
Submitter: FVD−1.33FVD motions get 73% lower odds
Submitter: SGP+0.99SGP motions get 2.7× higher odds
Submitter: JA21+0.93JA21 motions get 2.5× higher odds
Stylistic extremity−0.69Each point of extremity halves odds
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Who submits matters more than what the motion says. FVD motions systematically receive low centrist support regardless of content. SGP and JA21 motions do better. Higher rhetorical extremity and material impact both predict lower centrist support — centrist parties respond more to policy substance than to framing.

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What This Means

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The Dutch political landscape post-2024 is not best described as "the Overton window shifted right." A more accurate description:

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  1. Right-wing parties strategically moderated. They filed more motions, with milder content, framed in centrist-friendly language. The share of high-impact proposals (M≥4) dropped from 23.7% to 11.3%.
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  2. Centrist parties rewarded the moderation. Support surged from 0.251 to 0.507, driven primarily by CDA and ChristenUnie on migration issues.
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  3. The ideological divide held or widened. SVD spatial analysis shows centrists moved left on both axes while right-wing parties moved further right. The cultural gap widened by +0.146.
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  4. The effect may be temporary. Quarterly data shows centrist support peaked in 2024-Q4 (0.648) and has since reverted to 0.334 — below the pre-shift threshold.
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  5. Migration is the exception. The one domain where genuine acceptance expansion (not just content moderation) is measurable. Centrists went from never supporting M=5 migration motions to backing nearly 1 in 5.
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+The critical caveat: This analysis establishes a structural break in centrist voting behavior, not its cause. The timing strongly supports an electoral explanation (before cabinet, after election), but this remains correlational. A proper causal design would require comparison groups we don't have. +
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Methodology

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This analysis uses data from the Dutch Tweede Kamer OData API, covering 2,986 classified right-wing motions (2016–2026). Key methodological choices:

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Data sources: Dutch Tweede Kamer OData API, 2016–2026. All motion texts, voting records, and MP metadata.

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Code: Analysis scripts in analysis/right_wing/. Reports in reports/overton_window/.

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Reproducibility: All analyses are deterministic given the same database state. No LLM calls in the final pipeline (scoring was done once; analysis uses stored scores).

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