WASHINGTON, D.C. — People always remember their first presidential vote — their first participation in the largest decision of American democracy.

In high school, I was a rather awkward, nerdish history buff. (My wife would dispute the verb tense.) I was also something of a lefty, particularly compared with my conservative religious upbringing. I debated on behalf of Jimmy Carter in the mock election at my Christian high school during the 1980 election, making me a political minority of one.

But my political identification had begun to shift by 1984, and I cast my first presidential vote for Ronald Reagan. For me, exposure to economics had an ideologically sobering effect. (A young liberal can't be too careful in his or her reading.) In addition, Walter Mondale and his running mate, Geraldine Ferraro, had turned conservative religious people into a rhetorical skeet target. And Reagan himself — who had demonstrated personal courage and a capacity to govern — seemed to embody something hopeful and decent about the country.

I was not alone. In 1984, voters ages 18 to 24 supported Reagan over Mondale by 61% to 39%. "The oldest president in U.S. history and the youngest members of the nation's electorate," said the Philadelphia Inquirer in 1986 , "have forged one of the strongest bonds in American politics." The first serious political memories of my generation were of an appealing, creative, electorally dominant (at the national level) GOP.

Now jump forward to a recent USA Today/Rock the Vote poll that shows Hillary Clinton beating Donald Trump by 56% to 20% among voters under 35. Let that sink in. Trump is supported by 1 in 5 younger voters — an astonishing and consequential collapse for the GOP. Though the young don't turn out at election time with the same frequency as older voters, they always get (and deserve) particular attention from the parties. In the long run, younger voters are older voters. In the long run, older voters are . . . companions to John Maynard Keynes.

So why is Trump crashing and burning among the young? The 2016 election excludes some explanations. It cannot be that Clinton is making an inspiring, Barack Obama-esque appeal to youthful idealism. During the primaries, Clinton was routinely trounced among the young. In Iowa caucus entrance polling, Bernie Sanders bested Clinton among 17-to-29-year-old Democrats by 84% to 14% — the previous most laughable showing among the young.

And it cannot be that younger voters are rejecting Trump because he is too socially conservative. He got applause during his convention speech for promising to defend "LGBTQ citizens." Trump's nomination represents the advance of gay rights (though not of gay marriage) within the Republican coalition and the marginalization of social issues.

I would venture that Trump's failure among the young has something to do with his assault on the idea of tolerance, particularly racial and religious tolerance. Younger voters are less likely than other age groups to regard racially inclusive language as "politically correct." They are less likely to believe in "reverse discrimination" and to embrace anti-immigrant attitudes. And, according to the USA Today/Rock the Vote survey, they were not impressed by the GOP nominee's convention speech. By more than 2 to 1, younger voters said it made Trump seem less human and accessible.

While Clinton has an ethics problem, Trump has a humanity problem. His combativeness and lack of political polish could be advantages among younger voters. But these are tied to a discrediting lack of empathy. It is one thing to go after "low-energy" Jeb Bush or "Lyin' " Ted Cruz; it is another to mock a disabled reporter, stereotype Mexicans as rapists, condemn a judge because of his ethnicity, attack the faith of a grieving Gold Star mother, or call for systematic discrimination against Muslims. These are not violations of political correctness. They are violations of human decency, revealing serious moral impairment.

Here is something for Reince Priebus, Paul Ryan, Mitch McConnell and other Republican leaders to consider. At high schools and colleges with Latino or Muslim students, spray-painting "Trump 2016" on a wall or poster is properly taken as a racially charged incident. When white students chant "Trump! Trump!" at a basketball game against a team including minorities, it is properly taken as a racial taunt. Young people understand the logo of the Republican nominee — the very name of the Republican presidential candidate — as conveying a message of exclusion.

These are the first serious political impressions of my younger son, voting in his first presidential election this year. It is the way to lose a generation.