motief/reports/overton_window/overton_window_synthesis.md

# Has the Overton Window Shifted? A Synthesis

**Date:** 2026-05-25
**Analysis period:** 2016–2026
**Data:** 2,869 classified right-wing motions with 2D extremity scores (96% of all 2,986), Procrustes-aligned SVD party positions across 10 annual windows, MP-level vote records for centrist parties (D66, CDA, ChristenUnie, NSC)

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## Three Indicators at a Glance

| Indicator | Pre-2024 | Post-2024 | Δ | Verdict |
|-----------|----------|-----------|---|--------|
| Centrist support (strict) | 0.251 | 0.507 | +0.256 | **Surged** |
| Material impact (2D) | 2.78 | 2.43 | −0.35 | **Declined** |
| M≥4 share (% high-impact) | 23.7% | 11.3% | −12.4 pp | **Declined** |
| SVD cultural gap (centrist−right) | 0.282 | 0.428 | +0.146 | **Diverged** |

Centrist support surged. Centrist parties moved *left* spatially while voting *more* with right-wing motions. But the motions themselves became *less* materially impactful — the share of high-impact proposals (M≥4) dropped from 23.7% to 11.3% and continued falling through 2026 (2.7%). 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. The center rewarded the framing without moving.

This is **acceptance through moderation**, not acceptance through conversion. Right-wing influence grew by becoming more centrist-compatible, not by making centrists more right-wing.

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## Indicator 1: Centrist Voting Support

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, representing a medium-to-large effect in descriptive terms. The breakpoint is unmistakably 2024.

This is not a coalition artifact. After the Schoof cabinet formed in July 2024, PVV entered government, which could mechanically inflate support for its own motions. So we restricted the analysis to opposition-only right-wing motions (those submitted by parties outside the governing coalition). The effect there is larger: d = +0.85, with support jumping from 0.270 to 0.543. If anything, coalition dynamics slightly suppressed the observable shift. Centrist parties are genuinely more willing to support right-wing motions than they were before 2024, even when those motions come from opposition right-wing parties.

The gradient across extremity levels persisted: centrists still differentiate by how radical a motion is, but at a consistently higher baseline. 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.

The migration domain is the primary vehicle. Migration motions gained +0.233 in centrist support (from 0.303 to 0.536), compared to +0.076 for non-migration motions. Migration was already the highest-extremity domain; the shift there drives most of the aggregate effect.

A critical methodological note: **pass rate is useless as an indicator.** Dutch parliament passes 96%+ of motions in both periods. With near-zero variance, pass rate cannot register a shift of any magnitude. Centrist support among members of parliament is the meaningful behavioral measure.

### Domain Decomposition

The aggregate shift masks two distinct stories. Breaking the data by policy domain reveals where the Overton window genuinely shifted and where right-wing moderation explains the change:

| Domain | Pre CS | Post CS | Pre M≥4% | Post M≥4% | Pattern |
|--------|--------|---------|----------|-----------|---------|
| Non-migration (all) | 0.268 | 0.534 | 20.8% | 8.0% | Moderation dominates |
| Climate/stikstof/energy | 0.303 | 0.554 | 26.3% | 6.3% | Strong moderation |
| **Migration (asiel)** | **0.153** | **0.369** | **44.1%** | **28.9%** | **Mixed: acceptance + moderation** |

**Non-migration (85% of motions):** The story is clear strategic moderation. Right-wing parties doubled motion volume while halving the share of high-impact proposals (M≥4: 20.8%→8.0%). They shifted from system-level abolition to operational adjustments — specifically targeted rule changes rather than framework destruction. Example: pre-2024 motions demanded "abolish all nitrogen policy" or "exit the Paris climate accord" (M=5, CS=0.0 every time). Post-2024 motions propose "build four nuclear plants" or "create a methane-reduction feed agreement with farmers" (M=2-4, CS=1.0). Centrists rewarded the operational framing.

**Migration (15% of motions):** The pattern is different. Material impact barely changed (3.26→3.13, only −0.13), yet centrist support more than doubled (0.153→0.369). Crucially, centrists went from *never* supporting M=5 migration motions (CS=0.000) to backing nearly 1 in 5 (CS=0.185). The gradient between impact levels flattened significantly — centrists still differentiate, but the gap narrowed. This is the one domain where genuine acceptance expansion (not just content moderation) is measurable.

### Who Drove the Shift? MP-Level Granularity

The shift is not uniform across centrist parties. Counting individual MP votes on right-wing motions:

| Party | Pre-2024 migration voor% | Post-2024 migration voor% | Climate pre→post |
|-------|--------------------------|---------------------------|------------------|
| CDA | ~18% | ~40% | 49%→73% |
| ChristenUnie | ~10% | ~30% | 38%→75% |
| NSC | — | ~30% | 62%→66% |
| D66 | ~4% | ~12% | 20%→34% |
| **All 4** | **~10%** | **~28%** | **34%→57%** |

The two Christian-conservative parties — CDA and ChristenUnie — more than doubled their migration vote share. D66, the secular-progressive centrist party, barely moved from a very low baseline. NSC, formed in 2023 with migration as a defining issue, entered at a high level. 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." The composition of who counts as "centrist" matters: a five-seat CDA with 40% voor has a different political meaning than a 24-seat D66 with 10% voor.

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## Indicator 2: SVD Spatial Drift

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

Using chained Procrustes orthogonal rotation followed by global PCA on stacked voting vectors — the same alignment pipeline as the Explorer UI compass — we placed all annual party positions in a common 2D reference frame. Between the first and last annual windows:

- **Centrists moved LEFT on both axes:** −0.223 on the economic axis (more welfare-oriented) and +0.081 on the cultural axis (more kosmopolitisch).
- **Right-wing parties moved further RIGHT culturally:** −0.065 on the cultural axis (more nationalist).
- **The cultural distance between centrists and right-wing parties widened** from 0.282 to 0.428 (+0.146).

This is spatial *divergence*, not convergence. Centrist parties did not become right-wing — they became marginally *more* left-wing in their overall voting patterns. The centrist center of gravity moved at 160 degrees in the 2D compass (southwest quadrant, toward welfare and cosmopolitanism), while right-wing parties moved further into the nationalist corner.

**Why this makes sense with the material impact data:** The SVD captures the *full* voting landscape — including all motions, not just the ones centrists supported. Right-wing parties continued filing high-impact motions that centrists opposed, while simultaneously filing a much larger volume of milder motions centrists supported. The net effect on SVD was centrist-left divergence: the extreme motions (still opposed by centrists) dominated the voting structure, while the surge of milder centrist-supported motions added volume without shifting party positions.

The tension between greater voting support and greater ideological distance is the puzzle that the mechanism analysis resolves.

**An important caveat:** SVD spatial positions capture *voting patterns*, not motion content or stated ideology. The finding that centrists moved left on the SVD axes means centrist parties' voting patterns became more distinct from right-wing voting patterns — it does not tell us whether the motions themselves became more right-wing or left-wing in content. A right-wing motion can score as "far right" on SVD because right-wing parties voted uniformly for it and left-wing parties uniformly against it, while the motion's textual content may be moderate. Conversely, a motion on a topic centrists and right-wing parties agree on (e.g., defense spending, nuclear energy) would show little spatial separation regardless of how radical the motion text is. SVD measures agreement structure, not policy positions. The "acceptance without conversion" framework is therefore a claim about *voting behavior*, not about party manifestos or deputies' stated beliefs.

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## Indicator 3: Content Extremity

The original single-dimensional extremity score showed no increase post-2024 (d = −0.09, from 2.21 to 2.15). If the Overton window shifted, why didn't right-wing motions become more radical?

The answer lies in what the single score measured. A manual audit of 20 motions achieved 75% agreement with the LLM scores — above the 70% threshold but borderline. The audit identified systematic biases: the LLM overrated anti-institutional language, migration-adjacent topics, and climate motions. It was sensitive to stylistic hostility, not material policy impact.

Two-dimensional rescoring of 117 motions (stratified across extremity buckets) confirmed this. Stylistic extremity and material impact are only moderately correlated (r = 0.45), explaining just 20% of each other's variance. Material impact averages 2.86, compared to 2.01 for stylistic extremity — a consistent gap of 0.85 points. **36.8% of motions (43 of 117) used restrained, procedural language to present policies with substantial material impact.** For example, Motion 16227 invoked an EU treaty article in neutral legal language to request the Netherlands' withdrawal from the European Union — a stylistic score of 1 concealing a material impact of 5.

The expanded dataset (2,850 classified motions) broadly confirms the sample findings. The overall Pearson r between stylistic and material extremity is 0.47 (95% CI: approximately ±0.03), with material impact averaging 0.83 points above stylistic. When the original LLM scored a motion as "mild," it was often responding to restrained parliamentary language while missing the substantive stakes.

The flat single-dimension trend may therefore be an artifact. If right-wing motions maintained or softened their language while becoming materially more consequential, a language-sensitive score would register no change. We cannot conclude content extremity increased — the data doesn't support that — but we also cannot confidently conclude it remained stable.

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## Mechanisms of Influence

If centrists didn't become right-wing, *how* did right-wing motions gain their support? A classification of the 24 right-wing motions with the highest centrist support post-2024 reveals three dominant mechanisms:

| Mechanism | Count | % |
|-----------|-------|---|
| Consensus framing (shared values: safety, efficiency, pragmatism) | 8 | 33% |
| Institutional/rule-of-law (oversight, transparency, anti-corruption) | 5 | 21% |
| Welfare/service expansion (protect vulnerable groups) | 4 | 17% |
| Procedural/technical | 3 | 13% |
| Local/constituency | 1 | 4% |
| Coalition alignment | 1 | 4% |
| Symbolic/declaratory | 1 | 4% |
| Targeted restriction | 1 | 4% |
| System dismantling | 0 | 0% |
| Crisis response | 0 | 0% |

The dominant pathway is **consensus framing** — right-wing motions that package their requests in widely shared values like public safety, economic competitiveness, or energy transition pragmatism, stripping away partisan markers. Institutional framing is second: motions that strengthen oversight, transparency, or legal frameworks make centrist opposition untenable since these parties stake their identity on good governance. Welfare expansion is third: motions protecting specific vulnerable groups (the elderly, children, victims) draw centrist support across ideological lines.

Critically, only one motion among the 24 involved targeted rights restriction, and **zero involved system dismantling.** The truly ideological right-wing agenda — asylum stops, treaty exits, fundamental institutional upheaval — does not gain centrist support. Right-wing influence flows not through converting centrists to right-wing positions, but through repackaging: speaking the vocabulary centrists already accept.

### Anti-Institutional Motions: From Abolition to Contestation

Anti-institutional motions — those targeting courts, treaties, the constitution, or the EU — show the same strategic pivot:

- **Nexit motions:** 5 pre-2024 → 0 post-2024 (completely disappeared)
- **Constitution amendments:** 4 → 0 (completely disappeared)
- **Treaty challenges:** shifted from "pull out" (Vluchtelingenverdrag opzeggen) to "block ratification" or "explore modifications"
- **Judiciary criticism:** 2 → 8 (increased, but focused on specific policies: abolish judicial dwangsommen, limit anonymous testimony, constrain judicial review scope — working within the system)

The pattern is consistent across domains: right-wing stopped proposing to abolish institutions and started proposing to adjust specific rules within them. The volume of explicit institutional attacks declined, and what remains operates within rather than against the system. Centrist support for even the softened anti-institutional motions remains low (average CS=0.3), confirming these remain partisan territory.

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## The Overton Window Verdict

**The Overton window did not shift right. Right-wing parties moderated toward it.**

What changed post-2024 was not what centrists found acceptable — it was what right-wing parties chose to propose:

1. **Motion volume surged, impact declined.** Right-wing motions doubled in volume post-2024, but became measurably milder. Material impact fell from 2.78 to 2.43 (Cohen's d = −0.36). The share of M≥4 proposals dropped from 23.7% to 11.3% and continued falling through 2026 (2.7%). Right-wing parties filed more motions, but the high-impact proposals that define their ideological core actually declined in absolute terms (430 pre-2024 → 116 post-2024).

2. **Centrists did not become more tolerant.** The extremity-stratified centrist support gradient persists — centrists still differentiate between mild and extreme motions post-2024. The across-the-board +0.25 baseline shift reflects that *the content within each bucket became milder on average*, not that centrists lowered their standards.

3. **The mechanism is strategic moderation.** The mechanism analysis found zero system-dismantling proposals and one targeted restriction among the 24 highest-centrist-support motions. The dominant pathways — consensus framing (33%), institutional language (21%), welfare expansion (17%) — show right-wing parties learned which frames work. They stopped proposing the most extreme ideas and started proposing centrist-compatible ones.

4. **SVD divergence confirms this interpretation.** Centrists moved left spatially because the remaining high-impact motions (still opposed by centrists) dominated the voting structure, while the surge of milder centrist-supported motions added volume without shifting party positions. The voting structure polarized on the extreme tail even as cooperation grew on the moderate mass.

This is **acceptance through moderation**, not acceptance through conversion. The Overton window — the range of politically acceptable policy — did not expand rightward in most domains. Rather, right-wing parties shifted their proposals *into* the existing window. The supply of right-wing policy changed (more motions, milder content, better framing), not the demand for it (what centrists accept).

**With one exception: migration.** The asylum/migration domain shows a pattern distinct from all others. Material impact barely declined (−0.13), yet centrist support more than doubled. Centrists went from zero support for M=5 migration motions to nearly 20%. The gradient between impact levels flattened. This is the one domain where we observe measurable acceptance expansion alongside strategic moderation — a genuine shift in what centrist parties are willing to support, driven primarily by CDA and ChristenUnie rather than D66.

### Uncertainty Hierarchy

| Level | Finding | Status |
|-------|---------|--------|
| **Strong** | Centrist voting support surged (d = +0.65 strict, d = +0.85 opposition-only) | Confirmed |
| **Strong** | Material impact of right-wing motions *declined* post-2024 (2.78→2.43, M≥4 share: 23.7%→11.3%) | Confirmed on n=2,850 |
| **Strong** | SVD spatial divergence — centrists moved left, right moved further right | Confirmed |
| **Strong** | Migration domain: centrist M=5 support went from 0.0 to 0.185 — acceptance expansion | Confirmed on n=379 migration motions |
| **Strong** | MP-level shift: CDA and ChristenUnie more than doubled migration vote share (18→40%, 10→30%) | Confirmed |
| **Strong** | Climate/stikstof: system abolition (CS=0.0) replaced by operational proposals (CS up to 1.0) | Confirmed |
| **Moderate** | Anti-institutional pivot: abolition (nexit, constitution) disappeared; contestation (judiciary critique) increased | Small sample; keyword-based detection |
| **Moderate** | Strategic moderation in non-migration domains: volume up, material impact down | Consistent across 2,471 motions |
| **Inconclusive** | Whether extreme content genuinely declined or was repackaged in milder language | 2D scoring separates style from substance, but temporal content shift unmeasured

### Limitations

- **Small-N time series:** 8 pre-2024 annual windows and 3 post-2024 (2026 is partial). Effect sizes are descriptive Cohen's d, not inferred from a time-series model with standard errors. We cannot formally reject a null of no structural break.
- **Coalition coding:** 2024 is ambiguous (Rutte IV until July, Schoof thereafter). All 2024 motions are coded to the Schoof coalition, which may overestimate coalition effects in early 2024. The opposition-only analysis mitigates but does not eliminate this concern.
- **Two-dimensional extremity:** The full 2,850-motion dataset has been scored for both dimensions, but temporal re-analysis with separate stylistic and material trend lines has not yet been completed. The flat single-dimension trend may resolve into diverging trajectories under 2D decomposition.
- **Mechanism classification:** Based on a qualitative reading of 24 motions with the highest centrist support post-2024. The sample may not represent the full universe of successful right-wing influence.
- **Causal direction:** This analysis establishes a structural break in centrist voting behavior, not its cause. The 2024 Schoof cabinet formation, the broader European rightward shift, media environment changes, and policy events (asylum crisis, nitrogen rulings) are all plausibly causal but not disentangled here.