The tally of congressional Democrats calling for President Joe Biden to exit the 2024 election race soared past 35 on Friday afternoon, as the Biden campaign's co-chair said the president "is weighing what he should weigh, which is, who is the best candidate to win in November and to carry forward the Democratic Party's values."

Also Friday, Ohio Sen. Sherrod Brown, the Senate Finance Committee chairman, became the highest ranking member of Congress so far to ask Biden to end his reelection campaign. NBC News first reported Brown's decision.

"I agree with the many Ohioans who have reached out to me," Brown said in a statement. "At this critical time, our full attention must return to these important issues. I think the President should end his campaign."

Brown, a Democrat, is facing a competitive Senate race in Ohio, a state that former President Donald Trump won in both the 2016 and 2020 presidential elections.

Earlier in the day, a group of more than 50 former U.S. foreign and national security officials urged Biden to end his candidacy, among them Anthony Lake, who served as national security advisor under former President Bill Clinton.

"We strongly believe that ongoing concerns surrounding your continued candidacy and the growing likelihood of an electoral college victory for Donald Trump put your national security accomplishments – and our country and your legacy – at an unacceptable level of risk," the group wrote.

As of Friday late afternoon, roughly 15% of the Democratic House caucus had publicly said they want the party to have another nominee to face Trump, the former president and the Republican Party's current nominee, in November's election.

Sen. Chris Coons, the Delaware Democrat who co-chairs Biden's campaign, told reporters, "I am confident he is hearing what he needs to hear from colleagues, from the public."

Coons' comment contrasts with what he said just days after Biden performed poorly in a June 27 debate against Republican presidential nominee Donald Trump, raising concerns about the president's mental acuity.

"The stakes of this race couldn't be higher, and the only Democrat who's ever beaten Donald Trump is Joe Biden," the senator told ABC News on June 30.

"He is our candidate for November, and he has the best shot to beat him," said Coons, whose seat is from Biden's home state.

Coons in a social media post on Friday after his comments in Aspen, Colorado, wrote, "I fully support the President. He's told me he's in it to win it. I'm with him 100% because I know he can beat Trump just like he did last time."

Biden's other campaign chair, Jen O'Malley Dillon, on Friday brushed aside growing congressional Democratic calls for Biden to quit.

"You have heard from the President directly time and again: He is in this race to win, and he is our nominee, and he's going to be our President for a second term," O'Malley Dillon said in a statement.

Biden, who is isolated at his Rehoboth, Delaware, beach house with a Covid-19 infection, in his own statement Friday afternoon said, "I look forward to getting back on the campaign trail next week to continue exposing the threat of Donald Trump's Project 2025 agenda while making the case for my own record and the vision that I have for America."

"The stakes are high, and the choice is clear," Biden said. "Together, we will win."

But two people familiar with the situation told NBC News that members of Biden's family have discussed what his exit from the election race against Trump would look like if he makes that decision.

As of late Friday afternoon, more than 30 House Democrats and four Democratic senators had urged Biden to drop out.

Henrich and Brown joined Jon Tester of Montana, who made his announcement Thursday, and Vermont's Peter Welch.

The House members who had announced Friday that they wanted the party to select a new nominee were: Reps. Sean Casten and Chuy Garcia of Illinois, Zoe Lofgren and Jared Huffman of California, Marc Veasy of Texas, Mark Pocan of Wisconsin, Greg Landsman of Ohio, Betty McCollum of Minnesota, Florida's Kathy Castor, Morgan McGarvey of Kentucky and Gabe Vasquez of New Mexico.

Biden got a boost Friday when the political action committee arm of the Congressional Hispanic Caucus endorsed the 81-year-old's candidacy for reelection.

"This November, we will harness the power of our community to defeat Donald Trump and his Project 2025 agenda, and reelect President Biden," CHC Bold PAC said in a statement.

Earlier Friday morning, a Biden campaign memo obtained by NBC News said he will remain the Democratic presidential choice in November and that the party has "no plan for an alternative nominee."

"While voters consistently mention President Biden's age when contacted, our target voters — both reengagement and true swing voters — are still planning to vote for him, making it clear the debate has not hurt support among the voters who will decide this election," wrote Biden campaign battleground states director Dan Kanninen in the memo.

"He's the presumptive nominee, there is no plan for an alternative nominee. In a few short weeks, Joe Biden will be the official nominee," Kanninen wrote. "It is high past time we stop fighting one another. The only person who wins when we fight is Donald Trump."

During an appearance on MSNBC's "Morning Joe" show, O'Malley Dillon said, "I'm not here to say that this hasn't been a tough several weeks for the campaign."

"There's no doubt that it has been," O'Malley Dillon said. "And we've definitely seen some slippage in support, but it has been a small movement."

She spoke after Casten's editorial in the Chicago Tribune called on Biden to drop out, but before the other House Democrats joined that call.

This is developing news. Check back for updates.