“Joe Biden is our nominee,” she told a CBS News reporter outside a San Francisco fundraiser Tuesday night amid signs the president’s Democratic dam was breaking.

The reporter tried another tactic, asking if she was ready to lead the country if needed. Nothing.

“I am proud to be Joe Biden’s running mate,” she replied.

In the week since Biden’s disastrous debate performance, Harris has received more attention than at any time since her early, rocky days as his No. 2. Polls and party infrastructure give her an advantage over other possible Biden replacements, should he choose to step out of the race against former President Trump.

But Harris is in a delicate position — a magnified version of the political pressure she has faced throughout her tenure in office. She can’t afford to show even a hint that she is looking to replace Biden, the oldest president in history at 81. Yet she has to watch her back, to make sure others do not usurp her in the event Biden’s job becomes available.

“She absolutely, positively has to dance with the one who brought her, and any daylight that she shows between herself and the only person on Earth who could be called her boss would be seen as disloyal,” said one former advisor, who requested anonymity to avoid angering fellow Democrats with succession talk. “If ground keeps shifting … inevitably she’s going to be put in a position of potentially having to make a decision or maybe a decision’s being made for her.”

So far, she’s been earning relatively good marks from Democrats appreciative of her attempts to defend Biden, while Republicans continue to mock her public speeches as word salads.

“It’s been interesting to watch people who have been critical of her over the last three and a half years say, ‘Oh I’d support her,’” said an ally who is in regular contact with Harris’ and Biden’s inner circles, who asked for anonymity to avoid upsetting friends in Biden’s orbit. “People believe, and have always believed, she can prosecute the case.”

Harris went on CNN within minutes of last week’s debate, when most Democrats were still shell-shocked, offering the first version of Biden’s defense. She acknowledged what she called a “slow start” while insisting, “I’m not going to spend all night with you talking about the last 90 minutes when I’ve been watching the last three and a half years.”

Harris has made a similar case since then, traveling to speeches and fundraisers, including a Tuesday night event in San Francisco, in which she categorized the “elephant in the room” as both the debate and the prospect of another Trump presidency.

“She’s doing her job, and to suggest there is somebody waiting in the wings, somebody looking to get a jump-start on 2028 — no, that’s not Kamala Harris,” said Donna Brazile, an ally who wants Biden to stay at the top of the ticket.

Her sometime rival Gov. Gavin Newsom has taken a similar tack, positioning himself as a public defender for Biden, distancing himself from elements of the party who want the president to step aside. He was scheduled to visit the White House on Wednesday night to “stand with the president,” he said in a fundraising email.

Harris had her regular lunch with Biden on Wednesday. She also joined Biden on a campaign call in which he reassured staff that he was “in this race to the end,” according to a person familiar with the call who spoke on condition of anonymity. “We will not back down. We will follow our president’s lead. We will fight, and we will win,” Harris told the staffers, this person said.

Though Biden promised her weekly lunches when she took the job, the meetings have been inconsistent, an indication that Biden has often leaned more on longtime aides than on his deputy.

But if she were to run for president, she could campaign on the administration’s legislative successes, including its environmental and infrastructure spending bills.

Republicans would seize on her role as a key player in Biden’s immigration policy: Early in his tenure, Biden assigned Harris to oversee a strategy intended to bolster economic, security and political conditions in Central America to stem the “root causes” of migration.

But Harris has never been comfortable with the assignment, and Republicans have gleefully cast her as the “border czar” as they have attacked the Biden administration for record numbers of border arrests.

Harris gained political strength after the Supreme Court overturned the right to abortion in 2022, leading the White House’s response. She has been unable to change the law or to stop red states from passing extensive restrictions on the procedure, but she helped the Democratic Party use the issue to overperform in the 2022 midterm elections. Democrats are hoping to use the issue again if they can move beyond the concerns over Biden’s fitness for office.

A CNN poll released Tuesday found three-quarters of American voters believed Democrats would have a better shot at the White House without Biden. Among possible replacements, only Harris polled within 2 percentage points of Trump. Allies have long said her name recognition and control of the party apparatus would put her in a better position to lead than potential rivals, who include Newsom, Michigan Gov. Gretchen Whitmer, Pennsylvania Gov. Josh Shapiro and Minnesota Gov. Tim Walz.

Rep. James E. Clyburn (D-S.C.), who has been a pivotal Biden supporter, said Tuesday on MSNBC that he would support Harris as a replacement, but that his first preference is Biden remaining the candidate.

“But I want to support her going forward, sometime in the future,” he said.

But there remains deep concern about Harris in the party. Even the CNN poll showed her with ground to make up against Trump in a theoretical matchup, and that’s without the media scrutiny and Republican assault that would come with leading the ticket. And her early struggles in the job — which produced high staff turnover and low poll numbers — set a bad impression for many voters, though her average approval in polls has improved slightly in the last few months.

A March USA Today/Suffolk poll found that 54% of voters said she is not qualified to serve as president, compared with 38% who said she is. Focus groups shared with The Times by a pro-Biden Republican group earlier this year showed swing voters and even Black voters had negative impressions, some of which her allies believe were tied to her race and gender.

But even if Harris would have work to do, no other possible replacement has faced as much national scrutiny, possibly making them a higher risk for the party.

“She has been under that spotlight and has taken her lumps as a result,” said the former advisor. “No one can say she’s unknown at this point.”

Bierman reported from Washington and Wiley from San Francisco.