The UK Independence Party was central to the Brexit vote

One way to understand the Brexit result, in which the United Kingdom voted to leave the European Union, is to study which areas of the UK supported "Leave" and which supported "Remain." YouGov, for example, provided this analysis and map before last week's voting showing how support varied across the UK.

(YouGov)

I wanted to go deeper to explain this variation. Each local authority in the UK reported the percentages received by Remain and Leave. I gathered the percentage that voted for Leave, which is my dependent variable.

If the anti-immigration, anti-establishment arguments had a greater effect on eventual referendum outcome, then past support for the UK Independence Party (UKIP) or UKIP-friendly demographics should have had more substantive effect on the Leave vote than support for the more traditionally Euroskeptic Conservative Party.

To show the effect of UKIP’s anti-immigration appeals on the eventual Leave vote, I use two measures of support for UKIP: the vote share for UKIP in the most recent local authority election and the UKIP Demographic Favorability Index created by Matthew Goodwin and Caitlin Milazzo (the creation of their index is described in detail in appendix B of their book). The index ranges from 0 to 1 and is based on each local authority’s socioeconomic constitution. Higher values indicate greater potential support for UKIP1.

I also include the Conservative and Labour parties' share of the vote in the last council election, and a term interacting Labour support with the UKIP index. I restrict the analysis to English local authorities only, and include a dummy variable representing each of the London boroughs. The results are reproduced below, with the dependent variable the vote percentage obtained by Leave in the local authority.

Analysis of Brexit vote using STATA. Coefficients show the effect of a one-unit increase in each variable on the percentage of each district voting Leave. (David Parker)

The UKIP index, Conservative vote share, and UKIP vote share variables are all significant and positive predictors of a vote to leave the European Union. Importantly, the UKIP Demographic Favorability Index has the most substantive effect on increasing the Leave vote, while the percentage of the vote obtained by UKIP in the most recent council election has the second largest effect — an effect almost double the effect of the conservative vote share coefficient.

Support for UKIP — a proxy for anti-establishment, populist, and anti-immigration support — does a far better job predicting Leave than does local authority support for the Tories. If this referendum were about traditional Euroskepticism, then one might expect the relationship between Conservative Party vote share and the Leave vote to be much stronger than the relationship between the Leave vote and measures of UKIP support.

But the most fascinating finding is actually the interactive relationship between the UKIP index and the Labour share of local authority vote in the last election. The Labour vote share variable is significant and negative, but the interaction term is significant and positively signed. This essentially means that UKIP-friendly demographics provided Leave with an extra push in areas that have supported Labour in past council elections.

Put another way, the arguments made by UKIP were more effectively deployed in Labour-areas that were older, whiter, less educated, and with higher levels of constituents employed in blue-collar occupations.

The Leave campaign benefited from the groundwork laid by UKIP over the past several election cycles in local council elections — increasingly, elections won at the expense of Labour. Moving from a 91 UKIP index constituency with a Labour local council vote share of 53 to 12 percent reduced the predicted vote for leave by nearly 2 percentage points. Without support from traditional Labour areas, the Leave campaign could not have won — and it was the emotionally charged arguments employed by UKIP over repeated elections that seem to have made the difference.

Classically, UKIP took an issue neither party has addressed effectively — immigration — and used it to build a substantial third-party challenge. In the 2015 general election, UKIP supplanted the Europhilic Liberal Democrats as the United Kingdom’s third-largest party. The UKIP challenge may, in time, reorder considerably the British party system and the 300-plus union itself.

The analysis shown here suggests that the Brexit results were about much more than Euroskepticism as usual. Brexit was an anti-establishment, populist, and national convulsion against the forces of globalization. These are exactly the forces Donald Trump has marshaled to, against everyone’s expectations, capture the Republican nomination. And, to a lesser degree, it is the anti-establishment, left-behind voters to whom Bernie Sanders appealed during his campaign for the Democratic nomination.

Fearmongering, not rational discourse about a democratic deficit, propelled the UK out of the EU. And it is exactly the same that could thrust Donald Trump into the White House.

David C. Parker is an associate professor of political science at Montana State University. He is the author of Battle for the Big Sky: Representation and the Politics of Place in the Race for the U.S. Senate and The Power of Money in Congressional Campaigns, 1880-2006.

This post is part of Mischiefs of Faction, an independent political science blog featuring reflections on the party system. See more Mischiefs of Faction posts here.