WASHINGTON — Ten more congressional Democrats called on President Joe Biden to drop his reelection bid Friday, the most in a single day since a poor debate performance shook confidence among his fellow Democrats in his ability to win November’s election.

The 10 Democrats on Friday, the day after former President Donald Trump officially accepted his party’s nomination at the Republican National Convention in Milwaukee, brought the total to 31, increasing the pressure on Biden to withdraw from the race.

While no member of congressional Democratic leadership has publicly called for Biden to step down, several top Democrats who were either involved with handling Trump’s impeachment trials or with investigations into the Jan. 6, 2021, insurrection at the U.S. Capitol have raised their concerns, citing the former president’s threat to democracy.

California Rep. Adam Schiff, who was the lead impeachment manager in Trump’s first impeachment trial, called on Biden to drop out, saying in a statement that he had “serious concerns” about the president’s ability to win a second term.

And Maryland Rep. Jamie Raskin, who was a member of the House Select Committee to Investigate the Jan. 6 Attack on the U.S. Capitol, stopped short of explicitly calling on Biden to step down, but urged the president to reconsider whether he should remain in the presidential race.

Biden remained at home in Delaware with no public events scheduled after testing positive for COVID-19 on Wednesday evening.

In an interview on MSNBC’s “Morning Joe” early Friday, Biden campaign co-chair Jen O’Malley Dillon said the president remained “absolutely” in the race, even as a growing number of Democrats voiced unease about his ability to defeat Trump.

“Absolutely the president is in this race, you’ve heard him say that time and time again,” she said. “He is the best person to take on Donald Trump.”

But reports also surfaced Friday that Vice President Kamala Harris, a potential replacement for Biden if he takes the unprecedented step of withdrawing from a race less than four months from Election Day, was scheduled to speak by phone with top Democratic donors in the afternoon.

Harris did not respond to reporters’ questions at an appearance at a Washington ice cream shop Friday, according to a pool report.

And 10 more congressional Democrats, including more senior members than had previously broken ranks with the president, said Friday that Biden should step aside.

U.S. Rep. Sean Casten of Illinois wrote an op-ed in the Chicago Tribune.

Reps. Jared Huffman of California, Marc Veasey of Texas, Jesús “Chuy” Garcia of Illinois and Mark Pocan of Wisconsin wrote a joint open letter to Biden that they posted on social media.

The quartet represents important constituencies in the House Democratic Caucus.

Veasey is the first member of the influential Congressional Black Caucus, which has been among Biden’s staunchest Democratic backers, to join the call for him to step down. He is also a member of the moderate New Democrat Coalition.

Pocan is the co-chair of the Congressional LGBT Equality Caucus and a former chair of the Congressional Progressive Caucus.

Garcia is a member of the Congressional Hispanic Caucus.

U.S. Sen. Martin Heinrich of New Mexico and Reps. Greg Landsman of Ohio, Zoe Lofgren of California also released their own statements. Betty McCollum of Minnesota told the Star Tribune newspaper she wanted Biden step aside and allow Harris to lead the ticket with Minnesota Gov. Tim Walz as her running mate.

Rep. Morgan McGarvey, of Kentucky, posted a statement on X.

The calls came a day after Sen. Jon Tester, in a difficult reelection race in Montana, said in a statement to the Daily Montanan that Biden should withdraw.

Rep. Seth Moulton of Massachusetts, who was one of few Democrats who called on Biden to step down two weeks ago, expanded on his view in an op-ed Friday.

Moulton wrote in the Boston Globe that when he went on a June trip to Normandy to commemorate the 80th anniversary of D-Day, the president didn’t recognize him, despite their decade-long relationship.

“Of course, that can happen as anyone ages, but as I watched the disastrous debate a few weeks ago, I have to admit that what I saw in Normandy was part of a deeper problem,” Moulton wrote. “It was a crushing realization, and not because a person I care about had a rough night but because everything is riding on Biden’s ability to beat Donald Trump in November.”