The gains for the Democrats among the college-educated are only part of the story. The survey data also show Mr. Trump making modest gains over all among white men, about five points more than in 2012. The increase comes from white men without a college education; he is up 10 points with that group relative to Mr. Romney and up 20 from Mr. McCain’s margin in 2008.

This brings Mr. Trump’s advantage among white men without a college education to a whopping 37 points over Mrs. Clinton. This may also be a reaction to Mr. Trump’s words and actions, but the trend toward the G.O.P. among these men started before Mr. Trump’s candidacy, in gains for Mr. Romney in the 2012 election. If the party is expanding in this way, the data suggest Mr. Trump may be more the result of the shifting than the cause of it.

Among white women, however, the shift to Mrs. Clinton looks more episodic. Across both education groups, they moved away from Mr. Obama in 2012 relative to 2008. Is their return to the Democratic nominee in 2016 merely a reaction to Mrs. Clinton’s being the first woman to be nominated by a major American party or is it a reaction to Mr. Trump? Given how hard Mrs. Clinton had to fight for women’s votes in her own party primaries against Bernie Sanders, it seems unlikely that women are generally drawn to her because of their shared gender. It is more likely that Mr. Trump has driven them to her.