Gabriel Lenz, a University of California, Berkeley, political scientist, has written a book about what happens among voters when leaders change positions on issues. The book is titled “Follow the Leader?” which gives you a hint of how things turn out. On most issues, when candidates change their minds, supporters will mimic the change instead of abandoning the candidates. As the book description says, “In many cases, citizens first pick a politician and then adopt that politician’s policy views.”

But President Trump might also be wrong about this. Using similar methods to Mr. Lenz’s, Michael Tesler, a political scientist at the University of California, Irvine, has conducted research on long-held predispositions, like views about people who are “different from you.” Mr. Tesler found that voters are less likely to change those kinds of positions to follow their party leaders. Candidates who change their minds on straightforward policy issues like the tax rate are likely to see their voters change their minds on those issues. The same is not true for topics drawing on racial or ethnic attitudes.