The matchup between Mrs. Clinton and Mr. Trump is accelerating trends that were expected to unfold gradually but have, in 2016, emerged to jolt the electoral map. The parties are realigning along an axis primarily of educational achievement, but also of race. Democrats have been on the upswing with minorities, college-educated whites and younger voters, while Republicans are increasingly reliant on older whites, whites without a degree, or both.

This explains why Mr. Trump is looking for breakthroughs in states where non-college whites outnumber college-educated whites the most: Iowa (by 30 percent), Wisconsin (by 25 percent), Ohio (by 24 percent) and Nevada (by 18 percent).

Conversely, it explains why Mrs. Clinton maintains an edge in states where that margin is closer, like Virginia (2 percent) and Colorado (0.1 percent), and has a strong opportunity to win North Carolina (12 percent).

The Clinton campaign calculates that its candidate is likelier to prevail by “disqualifying” Mr. Trump — using ads to make the idea of voting for him socially unacceptable in professional suburbs — among additional well-educated voters (in states like North Carolina) than by holding on to working-class voters tempted by Mr. Trump’s populism (in states like Ohio).