What Trump supporters were doing before Trump

But that said, one word isn’t enough to summarize a whole set of motivations. In the U.K., people who are concerned about immigration levels also tend to be politically disaffected: They see elites’ support for immigration as a prime example of politicians’ abandonment of working-class constituents. That mix of attitudes helped vault the anti-immigration, Euro-skeptic United Kingdom Independence Party to the political stage in recent years. There is some suggestion that the same dynamic is at work in the U.S. At 0.70, Trump supporters were notably more likely to say in 2012 that “at present I feel very critical of our political system” than were future Cruz or Rubio backers (0.64 and 0.62).

What’s more, if you take the 40 percent of the GOP electorate that backs Trump and multiply it by the 30 percent or so of the electorate that identifies as Republican, you get around 12 percent of the U.S. population whose first choice is Trump. That’s just one percentage point off the 13 percent that UKIP won in the May 2015 general election.