President Biden’s stumbling performance in the debate against former President Donald J. Trump has some Democrats raising the possibility of nominating an alternative candidate and mulling over a roster of names. High on the list is, of course, Vice President Kamala Harris, whose status as Mr. Biden’s running mate might make her an easy candidate for delegates to turn to during a difficult moment. But a crop of Democratic governors and other figures are often mentioned, too.
A candidate switch would most likely require Mr. Biden to step out of the race, something his campaign says he has no intention of doing. And the risks are real. Some of the highest-profile potential stand-ins listed below have never endured the vetting and road test of a presidential race. There is a long list of candidates who looked great on paper and withered on the campaign trail.
“It’s not as easy as it sounds,” said Barbara Boxer, the former senator from California. “Being vetted for president is like no other vetting. We don’t know how these people would do.”
Here are a few of the contenders being discussed:
Kamala Harris
Vice President Harris, a former prosecutor and senator of California, has at times struggled to define her role at Mr. Biden’s side. Initially charged with addressing polarizing and intractable issues like illegal migration and voting rights, she has been viewed by Democratic donors and supporters of Mr. Biden as a potential political liability. Though those concerns have eased, she has been weighed down by low approval ratings that are barely higher than the president’s.
Still, Ms. Harris has for months stumped for the president as one of his main campaign surrogates. She has recently become the White House’s lead voice as a defender of abortion rights. In March, she met with abortion providers at a clinic in St. Paul, Minn., in what is believed to be the first visit by a president or vice president to an abortion clinic. And Ms. Harris, the nation’s first Black vice president, has worked to shore up Mr. Biden’s vulnerabilities with Black and young voters.
Democrats have long worried about how she might fare against Mr. Trump, though Ms. Harris has in recent months sharpened her attacks against the former president — particularly on abortion — in an effort to demonstrate she could hold her own against him.
Gavin Newsom
Gov. Gavin Newsom of California, the former mayor of San Francisco who also previously served two terms as lieutenant governor, has become one of Mr. Biden’s main surrogates during this campaign.
He was almost first out of the box defending Mr. Biden’s performance in Atlanta. He brings some clear benefits: He is an accomplished campaigner from a big state who has used his platform in Sacramento — and appearances on national television — to make the case against Mr. Trump and for the Democratic Party. He has not shown any reservations about Mr. Biden, but has waited on the sidelines in case Mr. Biden somehow did not end up on the ticket and, in any event, openly considered running in 2028.
But — California. For one thing, Mr. Newsom would be saddled with explaining the problems California has had over the past decade: homelessness, high taxes, escalating housing costs. He will probably never be able to escape his decision in 2021 to hold a high-priced dinner with lobbyists at the high-end restaurant the French Laundry.
All that said, should Mr. Biden decide to end his run, Mr. Newsom could benefit from the shortened campaign: It would offer less time for opponents to explore and amplify some of those potential shortcomings.
Gretchen Whitmer
Gov. Gretchen Whitmer of Michigan has risen quickly as a national star of the Democratic Party, helped in part by Mr. Trump’s antagonizing her as “that woman from Michigan.” A two-term governor, Ms. Whitmer led a 2022 campaign that gave Democrats in the battleground state a trifecta — exercising full control of the legislature and state government — for the first time in 40 years.
She has used that mandate to enact a laundry list of progressive policies. Her national profile also soared during the pandemic, when she was vilified by right-wing media and Republican officials for her lockdown measures. And Ms. Whitmer is a vice chair of the Democratic National Committee, a top leadership position in the national party.
For all of these reasons and more, she is near the top of nearly every Democrat’s list of strong candidates for 2028, and she has recently nodded to her post-Biden presidential ambitions. Most important, she comes from a swing state that likes her: She won re-election with more than 54 percent of the vote in 2022.
JB Pritzker
Gov. JB Pritzker of Illinois, the billionaire heir to the Hyatt Hotels fortune, has stood out as a Biden surrogate for his knife-twisting insults against Mr. Trump. When the former president was convicted in his New York criminal trial, Mr. Pritzker broke from the carefully worded talking points of most Democrats and hammered the former president as a felon, a racist, a homophobe and a grifter.
That fiery demeanor and his caustic attacks against Mr. Trump have earned Mr. Pritzker applause as he’s stumped for Mr. Biden across the Midwest. He also has a significant progressive record as a two-term governor, scoring notable victories on abortion rights and gun control, and he has shifted the state Democratic Party far from its traditionally center-left politics.
Josh Shapiro
Gov. Josh Shapiro of Pennsylvania, the former attorney general of the state, is known as a measured leader who has emphasized bipartisanship and largely focused on nonideological issues during his term in office.
Mr. Shapiro, who won the governor’s mansion in 2022, had a job approval rating of 64 percent in a recent survey, with just 19 percent of registered voters in the key battleground state saying they disapproved. In contrast, 41 percent of those surveyed said they would vote for Mr. Biden in November.
Mr. Shapiro often talks about his Jewish faith and has plunged into a fierce divide in the Democratic Party over pro-Palestinian student protests, passionately defending his support for Israel and denouncing some of the recent demonstrations as antisemitic.
But this is the most important thing to know about Mr. Shapiro: He is the governor of Pennsylvania. And if there is such a thing as a must-win state for any Democratic challenger to Mr. Trump, Pennsylvania would be it. Mr. Shapiro defeated his Republican opponent in 2022, Doug Mastriano, with 56 percent of the vote, a figure that is sure to be top of mind for Democratic delegates making this kind of decision.
Other Possibilities
This list is not exhaustive; the kind of chaos that could be unspooled at the Democrats’ convention in Chicago if Mr. Biden withdraws allows for all kinds of possibilities. Among the conventional ones: Transportation Secretary Pete Buttigieg and Senators Cory Booker of New Jersey and Amy Klobuchar of Minnesota. All three have run for president before and are familiar to Democratic voters.
Gov. Andy Beshear of Kentucky, who won re-election in 2023, has also gained national attention for his unlikely success as a Democrat in a red state where Mr. Biden is deeply unpopular. Mr. Beshear defeated his Republican opponent, Daniel Cameron, by five points, even as other Democratic candidates in statewide races lost by overwhelming margins.
And finally, two people who have already lived in the White House: Hillary Clinton and Michelle Obama. Former President Barack Obama, while still polling fairly high among registered voters, is barred by constitutional term limits from running for a third term.
