Former President Barack Obama has privately conveyed his worries to Democrats about President Joe Biden’s run for office, and Speaker Emerita Nancy Pelosi has privately cautioned that Democrats might lose their chance to gain control in the House if Biden doesn't withdraw from the race, according to several people familiar with the sensitive internal matters.

Pelosi also showed Biden polling that she argued shows he likely can't defeat Republican Donald Trump, according to two of the people, who insisted on anonymity to discuss such matters.

Obama has not spoken directly to Biden, two other people said. He has conveyed to allies that Biden needs to consider the viability of his campaign but has also made clear that the decision is one the current president needs to make.

Time racing, Democrats at the highest levels are making a critical push for Biden to reconsider his reelection bid, as unease grows at the White House and within the campaign at a fraught moment for the president and his party.

Biden has insisted he's not backing down, adamant he's the candidate who beat Trump before and will do it again. Pressed about reports that Biden might be softening to the idea of leaving the race, his deputy campaign manager Quentin Fulks said Thursday: "He is not wavering on anything."

In recent days the president has become more committed to staying in the race, according to another person familiar with the matter.

But influential Democrats from the highest levels of the party apparatus, including congressional leadership headed by Senate Majority Leader Chuck Schumer and House Democratic Leader Hakeem Jeffries, are sending signals of concern. Some Democrats hope Biden will assess the trajectory of the race and his legacy over the coming days.

Using mountains of data showing Biden's standing could wipe out the ranks of Democrats in Congress, frank conversations in public and private and now the president's own time off the campaign trail after testing positive for COVID-19, many Democrats see an opportunity to encourage a reassessment.

If Democrats are seriously preparing the extraordinary step of replacing Biden and shifting Vice President Kamala Harris at the top of the ticket, this weekend will be critical to changing the president's mind, other people familiar with the private conversations said.

One said it's now or never ahead of a planned virtual roll call to nominate the party's choice in early August, ahead of the Democratic National Convention in Chicago.

Over the past week, Schumer and Jeffries, both of New York, have spoken privately to the president, candidly laying out the views of Democrats on Capitol Hill, including Democrats' concerns.

Separately, the chair of the Democratic Congressional Campaign Committee, Rep. Suzan DelBene of Washington, spoke with the president last week armed with fresh data. The campaign chief specifically aired the concerns of front-line Democrats seeking election to the House.

And on Wednesday, California Rep. Adam Schiff, a close ally of Pelosi, called for Biden to drop his reelection bid, saying he believes it's time to "pass the torch."

Biden, in a radio interview taped just before he tested positive for COVID-19, dismissed the idea it was too late for him to recover politically, telling Univision's Luis Sandoval it's still early and many people don't focus on the November election until September.

"All the talk about who's leading and where and how, is kind of, you know – everything so far between Trump and me has been basically even," he said in an excerpt of the interview released Thursday.

Some national polls do show a close race, though others suggest Trump with a lead. And some state polls have contained warning signs for Biden, too, including a recent New York Times/Siena poll that suggested a competitive race in Virginia, a state Biden won in their 2020 matchup.

While the tensions over Biden's ability to carry on a winning campaign subsided some, particularly after last weekend's Trump assassination attempt and as the Republican National Convention is underway in Milwaukee, Democrats know they have limited time to resolve the party turmoil after the president's faltering debate performance last month.

To be sure, many Democrats want Biden to stay in the race. And the Democratic National Committee is pushing ahead with plans for a virtual vote to formally make Biden its nominee in the first week of August, ahead of the Democratic National Convention, which begins Aug. 19.

Late Wednesday, ABC News reported new details about Biden's private meeting over the weekend with Schumer at the president's beach home in Delaware. It said Schumer told the president it would be "better for the Democratic Party and better for the country if he were to bow out." A Schumer spokesperson called the report "idle speculation."

White House spokeserson Andrew Bates said Biden told Schumer, as well as Jeffries, that "he is the nominee of the party, he plans to win, and looks forward to working with both of them to pass his 100 days agenda to help working families."

But among Democrats nationwide, nearly two-thirds say Biden should step aside and let his party nominate a different candidate, according to an AP-NORC Center for Public Affairs Research poll. That sharply undercuts Biden's post-debate claim that "average Democrats" are still with him even if some "big names" are turning on him.

Biden tested positive for COVID-19 while traveling Wednesday in Las Vegas and is experiencing "mild symptoms" including "general malaise" from the infection, the White House said.

The president, who had spent the past several days campaigning, had already been scheduled to return to his Delaware beach home even before the diagnosis.

Schiff's announcement brings to nearly 20 the number of Democratic members of Congress calling on Biden to withdraw from the presidential race in the wake of his dismal debate performance against Trump last month.

Schiff said that by bowing out, Biden would "secure his legacy of leadership by allowing us to defeat Donald Trump in the upcoming election."

Schiff is a prominent Democrat on his own, and his statement will also be watched because of his proximity to Pelosi.

It was Pelosi who revived questions about Biden post-debate, when she said recently that "it's up to the president" to decide what to do – even though Biden had already fully stated he had no intention of stepping aside. The former House speaker publicly supports the president but has fielded calls from Democrats since debate night questioning what's next.

In response to Schiff's comments, the Biden campaign pointed to what it called "extensive support" for him and his reelection bid from members of Congress in key swing states, as well as from the Congressional Black and Hispanic caucuses. The campaign noted that Biden had been joined on his trip to Nevada this week by nearly a dozen Congressional Black Caucus members.