In his third attempt to run for president, Joe Biden found himself where he presumably has longed to be for decades: the front-runner for the Democratic nomination.

But during a nearly five-minute exchange with Senator Kamala Harris of California in his first debate of the campaign, he was verbally pummeled on busing policy and appeared unprepared to respond. He ended the exchange with possibly the best metaphor for himself and his front-runner status, “Anyway, my time is up.”

While Biden has not been the inevitable front-runner in the way that, say, George W. Bush was in 2000 or Hillary Clinton was in 2016, the exchange with Harris may have had the effect of instantly reshaping the 2020 Democratic presidential campaign.


To be sure, the race’s dynamics were already beginning to shift heading into Thursday’s debate. Biden’s lead over the rest of the field was dwindling. Vermont Senator Bernie Sanders, in second place, was slipping to Senator Elizabeth Warren, who had all the momentum. South Bend, Ind., Mayor Pete Buttigieg was holding his own, and Harris had largely stalled, though she still remained in the top tier.

But a week from now, polling could show a much different contest, largely because of the back and forth between Harris and Biden.

The moment was probably more damaging for Biden than it was positive for Harris. That’s because, according to polling, Biden entered the debate the front-runner mainly for three reasons: 1. He was well known. 2. He was perceived by Democrats as the most electable. 3. He has strong support among African-American voters.

While Biden will no doubt remain the best-known of the field for some time, his exchange with Harris may have created doubts among African-Americans about whether he can fully champion issues in the way Harris showed she can, and whether Biden can really go toe-to-toe against Trump if a first-term senator just owned him.


And the thing with crown of “electability” is that it’s ephemeral — once you lose that branding, it might be impossible to recover. After all, what is the pitch when Biden falls into second or third place? “I am the only candidate who can win, even though I am not actually winning”?

As for Harris, she could be on the rise after that exchange, but from where her support would draw could have its own implications. Would her momentum take away support from Buttigieg, the most recent “it” candidate? Would voters who want a woman to be president reconsider Warren and go with Harris? Will Harris convince some African-American voters that they have a shared lived experience and draw from Biden supporters?

Rarely do debates live up to the hype before or immediately after in terms of their impact on the race. Wednesday’s night debate among the first 10 candidates, for example, had some benefit to former housing secretary Julián Castro, but if any voters missed the debate, they didn’t miss a whole lot.

But Thursday could prove to be different, and the Harris-vs.-Biden moment could transcend the day-to-day fracas to be remembered as a pivotal early moment in the 2020 primary race.

James Pindell can be reached at james.pindell@globe.com. Follow him on Twitter @jamespindell or subscribe to his Ground Game newsletter on politics: http://pages.email.bostonglobe.com/GroundGameSignUp