Second, most so-called Reagan Democrats are actually Republicans today. The polarization of the parties, combined with modern electoral targeting techniques, means that we have seen increased political sorting since 1980. Mitt Romney won 93 percent of Republicans. Barack Obama carried 92 percent of Democrats. Very few voters cross party lines any more, especially in presidential elections. That said, there has been an unusually large number of voters switching parties for the primaries this year, but they appear to be split between Trump voters and those voting against him. There may also have been more than the usual number of mischief-makers trying to influence the Republican nomination process, especially early on, when it looked as if Hillary would be an easy winner on the Democratic side.

Of course, Trump’s campaign is probably not literally referring to Democrats who voted for Reagan. Rather, his team is talking about increasing the share of voters who are white and working-class. In particular, Trump hopes to attract large numbers of people who have not voted in recent elections but who fit into that category. But that’s a lot easier to say than to do.

In 1980, for example, even with all those Reagan Democrats, Ronald Reagan carried white voters by 10 percentage points. Mitt Romney actually won white voters by double that figure — 20 percentage points — but he still lost. That’s because whites’ share of the total vote fell from 90 percent in 1980 to around 76 percent in 2012. Even if Trump is able to push the white vote up by 2 or 3 points — something that he has shown that he is able to do in some primaries — he would still fall short in November. We live in a different demographic universe from the one we inhabited in 1980. And, while the absence of Barack Obama from the ticket could hurt minority turnout in some areas, the widespread antipathy for Trump among minorities would likely offset any falloff in the black or Latino vote.

Furthermore, all of this analysis presumes that Trump is able to hold traditional Republican votes, but that looks increasingly unlikely.