Eve, here. This post documents how voting systems interact with immigration policy, or more precisely anti-immigrant policy. The report notes that the majority voting system raises the bar for enforcing rules and laws restricting immigration. This is consistent with the US experience, which had a largely hard-coded two-party system until President Trump liberalized immigration.
By Matteo Gamalerio, assistant professor at the Barcelona University of Economics, Massimo Morelli, professor of economics and political science at Bocconi University, and Margherita Negri, senior lecturer at the University of St. Andrews. Originally published on VoxEU
Immigration has become one of the most salient issues in political debate. This column uses evidence from local elections in Italy to highlight the role of electoral rules in shaping immigration policy. Electoral systems that allow power to be won by a simple plurality of votes encourage the rise of anti-immigrant candidates and lead to more restrictive immigration policies. In contrast, systems that require an absolute majority of votes force anti-immigration parties into broader coalitions and lead to more open immigration outcomes.
Why do some democracies adopt stricter immigration policies than others? Voter preferences matter, but so do political issue salience (Gidron and Takeshi 2023) and the rules that turn votes into power. Recent research (Gamalerio et al. 2025) shows that when immigration becomes highly salient, as it has in recent years, electoral systems play an important role in determining whether anti-immigrant candidates enter the race and ultimately the policies that governments implement.
Weakening of the gap between left and right and the rise of immigration politics
For most of the postwar period, political competition in advanced democracies revolved around a single economic divide. The left favored redistribution and an expansive welfare state, while the right favored limited government and pro-market policies. Under these circumstances, policy outcomes can largely be explained by the logic of median voting. However, over time, confidence in both models has eroded. Fiscal crises, corruption, and weak public management undermined trust in state intervention, while globalization, automation, and financial crises undermined trust in free markets (Colantone and Stanig 2017, Autor et al. 2020, Guiso et al. 2025).
As the traditional left-right divide has become less salient, new issues have gained prominence (Tabellini 2019, Noury and Roland 2020, Gethin et al. 2022). Immigration, in particular, has become highly visible across Western democracies (Hatton 2021, Dennison and Geddes 2019, Schneider-Strawczynski and Valette 2025). Immigration combines economic concerns about jobs, welfare, and security with identity-based anxieties about culture and national cohesion (Mayda 2006, Dustmann and Preston 2007, Tabellini 2019), making it a powerful mobilizing tool for populist parties.
Figure 1 shows how migration flows have fluctuated significantly between OECD countries from 2000 to 2018, reflecting large differences in policy openness. Our study argues that these differences are not driven solely by preferences, but that the interaction between increasing immigration salience and electoral system design plays a central role.
Figure 1 Immigration in OECD countries
Note: OECD data on immigrant inflows per 1,000 inhabitants (2000-2018).
Sufficient plurality vs. necessary majority
We focus on an important feature of electoral systems: the percentage of votes needed to seize decision-making power. We distinguish between simple plurality systems, in which power can be won by a plurality of votes, and necessary majoritarian systems, in which a party or coalition must secure at least 50% of the electorate. The required majority voting system includes both proportional representation and dual voting, and requires an absolute majority to govern.
Our theoretical analysis yields three predictions. First, the required majority system makes it less attractive for anti-immigrant parties to operate independently. Second, these systems produce more open immigration policies than adequate plural immigration policies. Third, the difference between the two rules is greatest when opposition to immigration is neither very low nor very high.
Intuition is simple. If anti-immigrant sentiment is strong but less than 50% of voters, a single anti-immigrant candidate may win under a sufficient plurality, but not under a necessary majority. Anti-immigrant candidates are likely to win in either system if support is overwhelming. If it is very low, candidates have no incentive to campaign on an anti-immigrant platform, regardless of the electoral system.
We tested these predictions using Italian municipal data from 1993 to 2012.
local elections in italy
In Italy, public concern about immigration rose sharply in the 2000s. In 2002, only about 20% of Italians ranked immigration as a top issue, but by 2016 immigration had become one of the main issues across the political spectrum (Figure 2).
Figure 2 Salience of immigration in Italy
Note: Eurobarometer data on immigration salience in Italy (2002-2023). Blue: right-wing voters, red: left-wing voters, green: centrist voters, black: average including voters with no declared ideology. Self-reported ideology was not asked in 2012-2013.
Since 1993, mayors in Italy have been directly elected. When the population of a municipality exceeds 15,000 people, the electoral system changes rapidly from a plurality rule (sufficient plurality system) to a dual voting system (necessary majority system) (Bordignon et al. 2016). We exploit this institutional threshold to identify the causal effects of different electoral systems through a regression discontinuity design.
Election rules, anti-immigrant candidates, and local policy
Mayoral candidates in Italy are supported by one or more lists of city councils. These lists represent national parties, coalitions, or local political organizations (liste civiche). Using information about the political parties associated with each list, we investigate how electoral rules affect the likelihood that independent anti-immigrant candidates will enter the race.
Figure 3 shows the results. When the electoral system used to elect mayors switches from multiple voting to double voting, the probability of observing a candidate supported only by anti-immigrant parties drops sharply (by about 3.5 percentage points) (left panel). At the same time, the probability that an anti-immigrant party forms a coalition with a moderate center-right party increases by about 6.6 percentage points (right panel). In other words, the necessary majoritarian system forces anti-immigrant parties into broader (and more moderate) coalitions rather than allowing them to run independently.
Figure 3 Effect of double voting on mayoral candidate entries
Now we turn to the political consequences. Using data on procurement contracts (Pulejo 2025), we construct three measures of pro-immigration policies. Average number of procurement contracts for migration-related goods and services concluded by municipal governments during the election period. On average, local government spending during election periods goes toward welfare goods and services aimed at foreigners.
Figure 4 shows that all three indicators rise sharply as electoral systems move from plural voting to dual voting. Municipalities using dual voting are approximately 10 percentage points more likely to provide migration-related services (baseline: 19.8%). We win an average of 0.134 additional contracts per election period, which corresponds to an approximately 104% increase compared to the baseline average of 0.129 contracts. And it shows that immigration-related spending has increased by about 138%.
Figure 4 The impact of double voting on immigration policy
Finally, we examine how these effects vary by anti-immigrant sentiment. Using the vote share of anti-immigration and far-right parties in European elections from 1994 to 2009 as a proxy for opposition to immigration within municipalities, we divide the sample into tertiles (excluding municipalities above 0.50 due to lack of data) and examine how the effects of electoral systems differ across the three groups. Consistent with our theoretical predictions, we find an effect only for the third tertile where opposition to migration ranges from 0.198 to 0.494.
Beyond Italian municipalities: parliamentary elections and transnational evidence
Our findings extend beyond mayoral elections and have clear implications for parliamentary government systems. A simple extension of our model suggests that countries that elect their parliaments through a sufficient plurality system (e.g., “first-past-the-post”) tend to adopt more restrictive immigration policies than countries that adopt a necessary majority system (e.g., pure proportional representation). This prediction is consistent with the evidence for each country in Figure 5, which shows immigrant inflows per 1,000 inhabitants across countries whose parliaments are elected on the basis of sufficient plurality rules or necessary majority rules.
Figure 5 Transnational evidence: Sufficient and necessary majorities
Note: Data is provided by the OECD and covers 37 countries from 2000 to 2018. The graph compares countries with (NM) electoral systems to countries with (SP) electoral systems and examines the total inflow of immigrants per 1,000 inhabitants.
conclusion
Immigration is now a defining issue of political competition. Our research shows that electoral systems shape how this issue is reflected in policy. A simple plurality vote system would encourage the emergence of independent anti-immigration parties and lead to more restrictive immigration policies. Systems that require an absolute majority tend to force broader, more moderate coalitions and produce less restrictive immigration policies.
As political debate continues to be driven by identity-based issues, institutional design will continue to be a key determinant of democratic outcomes.
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