An internal rebellion aimed at forcing Joe Biden from the U.S. presidential race continued through the weekend, defying his effort to stamp it out.

Calls for his resignation spread even as he stepped up his public schedule following a sit-down interview with ABC News widely viewed as non-damaging, if unremarkable.

The list of congressional Democrats now publicly calling for Biden to withdraw grew to five over the weekend, but numerous others are saying it privately, including several more at a meeting on Sunday.

It's the lingering fallout from a catastrophic debate performance that has fuelled fears about the president's ability to wage an effective campaign leading up to the Nov. 5 election.

The situation will come to a head this week as lawmakers gather back in Washington, returning from the recess for Independence Day and seeking a path forward for their party.

In a sign of Biden's political viability teetering on a knife's edge, a number of Democrats are taking a non-committal approach — refusing to say whether they want him to run.

California Rep. Adam Schiff, for example, said that Friday's 22-minute ABC interview was not enough to quell the doubts.

"The interview didn't put concerns to rest," he told NBC's Meet the Press on Sunday.

"Joe Biden is going to need to consider, for his own sake and his own legacy: Can he beat Donald Trump? Is he the best to beat Donald Trump?"

Schiff's advice to Biden: Listen to a wider circle of people, beyond family and loyal staff, and talk to the party's best pollsters about whether he can beat Trump.

"Make the best informed judgment," the congressman said. "If the judgment is 'Run,' then run hard and beat that S.O.B."

A big week ahead

Most polls show Trump with his largest leads ever. Some still show a close race, with Biden even gaining. But concern about the potential down-ballot effect of a Biden wipeout has prompted congressional candidates to express alarm.

One swing-district Democrat in Minnesota joined the calls for the president to step down, saying she doesn't believe he can win. And there's reportedly an effort by a Democratic senator to organize a public show of dissent.

Tim Ryan, a former Democratic congressman, called this the decisive week, saying donors and party activists are worried that Biden's presence in the race could damage candidates running for the Senate and House of Representatives.

WATCH | Joe Biden refuses to pull out of presidential election campaign:

Biden refuses to withdraw from presidential campaign

In an exclusive interview with ABC News anchor George Stephanopoulos, U.S. President Joe Biden refused to entertain the question of what he would do if his closest allies shared concerns the Democrats would lose the House and Senate if he were to remain in the presidential race. 'It's not gonna happen,' he said.

"I think you're going to see a significant amount of pressure," Ryan, a former Ohio lawmaker, told Fox News Sunday.

"Sometime this week as the members come back [to Washington], this may be untenable for them to all run under a Biden ticket.... It's going to drag everybody else down."

While some have made public demands for Biden to step aside, the private sniping is worse. One adviser to large donors told the Washington Post that for every 10 people who think Biden should quit, one wants him to stay in the race.

The New York Times even quoted an anonymous senior White House official, who has worked for Biden for years, saying they have now reached the conclusion that Biden should drop out because he's no longer up to the task of vigorous campaigning.

The more common public line from Democrats is non-committal.

Connecticut Sen. Chris Murphy is among those in wait-and-see mode; he said Biden must prove quickly that he can maintain the pace of a campaign.

WATCH | When did Joe Biden lose the debate to Donald Trump?:

The exact moment Biden lost the debate | About That

U.S. President Joe Biden's performance during the first presidential debate against Donald Trump of the 2024 election campaign has raised questions from supporters and critics alike about whether Biden should withdraw from the race. Andrew Chang zeroes in on the critical moments that may have lost Biden the debate — and possibly his base.

Murphy said Biden must demonstrate this over the coming days with challenging events, like the press conference he's planning during this week's NATO summit in Washington.

"And if he can't do that, then he's got a decision to make," Murphy told CNN's Sunday morning politics show.

"This cannot be a business-as-usual week. Friday night's interview did not answer all the questions that people in my state have.... The clock is ticking."

Biden has support of Bernie Sanders

The fundamental reality for these skeptical Democrats is that Biden cannot be easily replaced; he can only be pressured to resign on his own, so that the party convention might crown a replacement, likely Vice-President Kamala Harris.

The president, however, sounds determined to fight on.

In his interview with ABC's George Stephanopoulos on Friday, Biden suggested that only direct intervention from above would convince him to drop out: "I mean, if the Lord Almighty comes out and tells me that, I might."

He was asked what he would do if he came under pressure from the party's major congressional leaders, such as Hakeem Jeffries, Chuck Schumer, Nancy Pelosi and James Clyburn. Biden did not directly answer.

But these party heavyweights, in fact, have not placed such pressure on him. In fact, some Democrats say they're hearing from voters of theirs who want Biden to stay.

The president is said to be counting on that sort of public reaction to quell the rebellion.

He just got an assist from perhaps the most prominent progressive in the country — Bernie Sanders, who ran against Biden for the 2020 presidential nomination.

Sanders, an Independent senator from Vermont, said his friend and onetime nomination rival can win. To do that, Sanders said, Biden must focus on a clear message for his second term aimed at the working class, such as promising to restore a child tax credit within 100 days.

"What we are talking about now is not a Grammy Award contest for best singer," Sanders told CBS's Face the Nation.

"Biden is old. He's not as articulate as he once was. I wish he could jump up the steps on Air Force One. He can't. What we have got to focus on is policy."

Counting on grassroots backing

Sanders's view is hardly unique: Even a Democratic strategist who said he wants Biden to drop out told CNN that on his radio show, he's overwhelmed by calls from his African American listeners for the president to keep fighting.

There was an example of that on Sunday when Biden attended a Black church in Philadelphia, Mount Airy Church of God In Christ. Bishop J. Louis Felton said God had changed the president's schedule, allowing him to be there for the service, because God knows Biden needs some love right now.

As the congregation stood and clapped, Felton went on to compare the president's political tribulation to the biblical story of Joseph being tossed into a pit.

"Never count Joseph out," he said. "You've lost a wife [in a car accident]. You've lost children. But God has never left you alone.... Even when Joseph is in the pit, don't count him out."

The bottom line is the debate within the Democratic Party is not settled.

"I'm hearing lots of things. I don't think this is as clear-cut as anybody wants it to be," Michigan congresswoman Debbie Dingell told CNN on Sunday.

"I've had people in [July 4th] parades shout at me, 'Tell him to stay! We have his back!'" Is she also hearing the opposite? "Of course," Dingell replied. "There are a lot of very strong opinions out there."

One thing she's adamant about? This can't go on much longer. "We're in our circular firing squad. We need to get out of it and start talking about [beating Donald Trump]."