Brandon Pennsylvania was the canary in the coal mine for Mr. Trump’s candidacy, reflecting both his opportunities (with noncollege whites who were skeptical of Romney) and his serious disadvantages (his demeanor and statements driving away suburban moderates, particularly women). If he couldn’t carry Pennsylvania because either a) he couldn’t turn out enough noncollege whites to outweigh losses in the suburbs or b) he couldn’t persuade enough college-educated whites he’s not nuts, then he wasn’t going to win the presidency. It was a matter of math and voting blocs.

You could have gotten Trump to 266 electoral votes with Iowa, Nevada, Ohio, Florida, all of the Romney states, and Maine’s Second District, but without Pennsylvania, where could he hit 270? He’s not winning Colorado, which has a Democratic plurality in voter registration for the first time in decades — and its Denver suburbs rejected Cory Gardner in a wave year. He’s not winning Wisconsin, where Republicans rejected him strongly back in April and barely favor him over Clinton in the Milwaukee suburbs. New Hampshire has plenty of independents but many of them are moderates, and his polling there was worse than it was in Pennsylvania. There was no alternative.

More college-educated voters, wealthy voters and suburban voters are drifting away from the Republican Party, while noncollege whites and residents of rural and exurban areas are moving toward it. Diversity has hit the suburbs themselves: Once overwhelmingly white, the inner suburbs of Philadelphia, in Delaware and Montgomery and Bucks, have seen an explosion in nonwhite residents, just like they have in Virginia, California, Colorado, Illinois, Michigan, heck, nearly everywhere.