Why do we keep talking about Joe Biden's age?

Is Joe Biden too old to be president?

I don’t know. But here’s what I do know: The question speaks volumes about the way Americans look at old age. It’s seen as a weakness that we unfairly ascribe to millions of people. And that prejudice enfeebles all of us, no matter how old we are.

Witness the hand-wringing about Biden, 76, who would become our oldest president if elected. Bernie Sanders is a year older, but his Feel-the-Bern popularity among younger voters seems to have insulated him from the seniority issue. And Donald Trump is, well, Donald Trump: Although he’s already the oldest American to become president, critics are less likely to attribute his lies, exaggerations and bizarre tweets to his age (73) than to his character.

By contrast, Biden has faced a drumbeat of skepticism about whether he’s too old for the job. Part of it has been fueled by Trump, who has charged that “Sleepy Joe” (as our inimitable president calls him) is “even slower than he used to be.” But there’s no real evidence for that.

Sure, the former vice president recently mixed up Theresa May and Margaret Thatcher. But he’s always been something of a “gaffe machine,” as Biden himself has playfully admitted. In 2008, he said “jobs” is a “three-letter word” and introduced his running mate as “Barack America.” He also asked a Missouri state senator to stand up and be recognized at a rally — which would have been fine if the legislator weren’t a paraplegic.