The force of demographic change largely explains why. Trump last November carried a crushing two-thirds of white voters without a college education—exactly as much as Ronald Reagan in his 1984 landslide and more than any Republican in between. But while Reagan’s dominance among blue-collar whites won him nearly 59 percent of the popular vote, it brought Trump just 46 percent; Reagan swept 525 Electoral College votes, Trump 306.

That erosion reflects two critical changes, each of which pressures Trump to attract more minorities. One is that the number of working-class whites—the group most drawn to Trump—has steadily declined. They constituted nearly two-thirds of all voters in 1984 but just over one-third in 2016, according to media exit polls. (The Census Bureau surveys that provide an alternative measure of voter demographics have put blue-collar whites at slightly above 40 percent, but show the same decades-long decline.) The second change is that Trump’s bellicose nationalism provokes much greater resistance than Reagan faced among college-educated whites, whose numbers have steadily increased since the 1980s. Reagan carried those white-collar whites by 24 percentage points, Trump by just three.

In office, Trump has continued to sharply divide whites along the diploma line. Figures provided by Gallup show that in an average of their daily tracking poll from mid-February to mid-March, a robust three-fifths of whites without a college degree approved of Trump’s job performance, compared with just two-fifths of whites with such a degree. That’s much less support than Republicans usually draw from college-educated whites, and a central reason his overall approval numbers are so unusually low.

Over time, a Trump-style GOP will likely need more backing from working-class minorities to offset both the entrenched resistance from white-collar whites and working-class whites’ inexorable contraction in the electorate. But so far, Trump has posted little progress among blue-collar black or Hispanic voters. In 2016, according to exit polls, Trump drew just under 30 percent from both college- and non-college-educated Hispanics, and won only 7 percent of non-college-educated African Americans. (That’s even slightly less than his 10 percent showing among blacks with degrees.) The Gallup tracking-poll average through mid-March found him drawing positive job ratings from only about one in six non-college-educated African Americans and just one in five Hispanics without degrees.

Veteran Democratic pollster Stanley Greenberg, though, found a larger potential opening for Trump’s message when he gathered focus groups to watch the president’s congressional address in late February. Greenberg, who convened the groups for the liberal organization Women’s Voices Women Vote Action Fund, found that minorities listening to the speech emerged significantly more open to Trump.