In the aftermath of Vice President Kamala Harris’ decisive electoral loss to former President Donald Trump, my mind has kept going back to a memorable and widely repeated gaffe by a man who was not on the ballot.

That man was Joe Biden, and the unfortunate utterance in question happened more than four years ago when he was a former vice president vying to unseat Trump.

The comment came near the end of a May 2020 interview with Charlamagne Tha God, co-host of “The Breakfast Club,” a popular syndicated radio show.

When Charlamagne invited Biden to the program’s New York City studio for another interview, mentioning that “we’ve got more questions,” Biden replied jovially, “You’ve got more questions? Well, I tell you what, if you have a problem figuring out whether you’re for me or Trump, then you ain’t Black.”

I am sure Biden would prefer never to hear that offensive and regrettable quote again, but it stands out from the other gaffes for which he is well known in the way it illustrated one of the biggest challenges he faced in his 2020 candidacy — and indeed the challenge the Democratic Party has struggled with since the close of the Obama era. Simply put, the party takes for granted the continual support of the voting blocs that have composed its coalition for at least a half-century.

In 2020, with Election Day approaching, Biden’s line was no laughing matter to his campaign. Instead, it became another brick in his backpack as his record of support from black voters as President Barack Obama’s former running mate turned wobbly.

Biden was deeply unpopular in July of this year when the Democrats jettisoned him from the presidential race in favor of Harris. To the surprise of many, she quickly closed the gap in party support in public opinion polls, and the Democrats pulled off a largely successful convention in Chicago. Up until Election Day the race remained a toss-up, depending on whose polls you believed. But then Trump pulled off a victory more decisive than his 2016 win Hillary Clinton.

And now the blame game has begun. Everyone who followed the contest on any level seems to have their own pet reasons for why defeat was snatched out of the jaws of victory.

Democrats have been here many times before. Barack Obama’s resounding victories in 2008 and 2012 lulled many of the party faithful to believe they had figured out how to avoid such disasters and the circular firing squad that inevitably followed. But now it’s autopsy time again.

The most positive thing you can do after a defeat is to learn from it — and the Dems, like any party in defeat, still have a lot to learn, particularly about some demographic groups fast rising in prominence and significance, particularly Hispanic Americans and young white males without college degrees.

I began writing about the impact of young non-college whites after Trump’s first election brought out that group, which has a history of low electoral participation.

While conventional politicians may pay less attention to those who don’t bother to vote, Trump, like the seasoned salesman he is, saw political pay dirt in this group of persuadable voters who simply hadn’t been brought off their sofas.

Exit polls found them to be frustrated yet attracted by Trump’s economic populism, even though his threats to raise tariffs and launch mass deportations of illegal migrants, if carried out, could lead to more inflation and to recession, precisely the economic factors many stated as their reasons for voting for the Republican.

Nonetheless, at least for now, such technical considerations don’t dim the enthusiasm of Trump’s MAGA crowds.

While Harris promoted her jolly version of the politics of joy, Trump undermined the Democrats’ coalition by pressing his own brand of the politics of grievance.

Harris and many other Democrats did little to explain the very real economic benefits the Biden-Harris administration brought to communities across the country, preferring instead to campaign on the threat Trump poses to women, minorities and the rule of law.

Although women and minorities still preferred Democrat Harris, early data from AP VoteCast, a survey of more than 120,000 voters nationwide suggests that Trump made some significant gains among these groups.

Large majorities of Black voters of both genders, long the Democrats’ most reliable base, favored Harris, as did narrower majorities of Latinos (but not Latino men), Asian Americans and those who identified as “non-white.” But members of all these demographic groups showed increasing defection to Republican ranks.

Pollsters find them to be attracted by religious affiliations and social conservatism, and there is no reason to believe this trend will not continue. For years, I have written that social conservatives have been missing a welcoming audience in Black churches and religious community organizations, who tend to be interested in private school vouchers and the like.

But the more unexpected trend in the long run (although perhaps not to those of us who have raised male children) is the rise of the “bro vote,” the Gen Z males who have made the macho podcast of Joe Rogan, among others, an almost required campaign stop for candidates. Even Trump’s son Barron has been enlisted into the cause as an adviser, according to the Trump campaign.

What emerges is an unflattering picture of one party desperate to hang on to its constituents facing another party that is in growth mode. Whatever else Trump’s GOP may be, it is a party unafraid to try new platforms to attract those who are either disaffected with politics or who had never been reached out to before.

The Democrats have a lot to learn from this defeat that should never have been, and the first lesson is to stop taking voters for granted.

— Clarence Page is a columnist and Washington-based member of Chicago Tribune’s editorial board.