WASHINGTON — President Joe Biden, in an open letter to congressional Democrats, stood firm Monday against calls for him to drop his reelection candidacy and called for an end to the intraparty drama that has torn apart Democrats since his dismal public debate performance.

Biden’s efforts to shore up a deeply anxious Democratic Party came as lawmakers returned to Washington confronting a choice: Work to revive his campaign or try to edge out the party leader, a make-or-break time for his campaign and their own political futures.

Biden wrote in the two-page letter that “the question of how to move forward has been well-aired for over a week now. And it's time for it to end.” He stressed that the party has “one job,” which is to defeat presumptive Republican presidential nominee Donald Trump in November.

“We have 42 days to the Democratic Convention and 119 days to the general election,” Biden said in the letter, distributed by his reelection campaign. “Any weakening of resolve or lack of clarity about the task ahead only helps Trump and hurts us. It's time to come together, move forward as a unified party, and defeat Donald Trump.”

Anxiety is running high as top-ranking Democratic lawmakers are joining calls for Biden to step aside despite his defiance. At the same time, some of the president's most staunch supporters are redoubling the fight for Biden's presidency, insisting there's no one better to beat Trump in what many see as among the most important elections of a lifetime.

Biden followed up the letter with a phone interview with MSNBC’s “Morning Joe” show, in which he insisted that “average Democrats” want him to stay in the race and said he was frustrated by the calls from party officials for him to step aside.

“They're big names, but I don't care what those big names think,” Biden said.

He threw the gauntlet at his critics, saying if they're serious they ought to “announce for president, challenge me at the convention” or rally behind him against Trump. Later, Biden joined a call with members of his national finance committee, while first lady Jill Biden campaigned for her husband in a three-state swing focused on engaging veterans and military families.

“For all the talk out there about this race, Joe has made it clear that he's all in,” she told a military crowd in Wilmington, North Carolina. “That's the decision that he's made, and just as he has always supported my career, I am all in, too.”

Democratic voters are split on whether Biden should remain the Democratic Party's nominee for president, or whether there should be a different Democratic nominee, according to a New York Times/Siena College poll.

More voices spoke up Monday, including the chair of the House's Congressional Progressive Caucus, Rep. Pramila Jayapal, who was not ready to cast aside Biden, saying that the threat of a second Trump presidency remains too high. Yet one of the most endangered Democrats this election cycle, Sen. Jon Tester of Montana, said in a statement, “President Biden has got to prove to the American people — including me — that he's up to the job for another four years.”

However, Biden's letter left some House Democrats, who want to hear directly from Biden himself, furious, according to one House aide granted anonymity to discuss the situation. Lawmakers particularly bristled at being cast as out of touch with voters since representatives in particular have been home in their districts listening to voters.

Biden planned to meet virtually Monday with the Congressional Black Caucus — one of his staunchest blocs of supporters in Congress. The White House would not say whether Biden would meet with all Democratic lawmakers in person at the Capitol this week.

Meanwhile, press secretary Karine Jean-Pierre said Biden had undergone three neurological exams while in the White House as part of his annual physical exams — and no more — and said the president has not been diagnosed with or treated for Parkinson's.

It's a tenuous and highly volatile juncture for the president's party. Democrats who have worked alongside Biden for years — if not decades — and cherished his life's work on policy priorities are now entertaining uncomfortable questions about his political future. And it's unfolding as Biden hosts world leaders for the NATO summit this week in Washington.

The drama is playing out with just over a month until the Democratic National Convention and just a week before Republicans gather in Milwaukee to renominate Trump as their presidential pick. Many Democrats are arguing the attention needs to be focused not on Biden but on the former president's felony conviction in the hush money case and pending federal charges in his effort to overturn the 2020 election.

In an effort to “get on the same page,” House Democratic leader Hakeem Jeffries is convening lawmakers for private meetings before he shows his own preference, according to a person familiar with the situation and granted anonymity to discuss it. He planned to gather on Monday some Democrats whose bids for reelection are most vulnerable.

Rep. Adam Smith of Washington the top Democrat on the Armed Services Committee, went public Monday with his call for Biden to step aside, saying it would be “a mistake” if Biden continues his campaign. “I'm calling on President Biden to step down,” Smith said on social media.

Biden's allies said they expected more direct engagement from the president with lawmakers — like the CBC virtual meeting — as he scrambles to shore up his candidacy. On a call Saturday with his campaign co-chairs, Biden repeatedly asked them, who else needs to hear from him, who else he needs to engage with and who still has unanswered questions or concerns, according to Sen. Chris Coons, D-Del.

“He is out there doing his job as a candidate and doing his job as president,” Coons said.

Senate Majority Leader Chuck Schumer would not answer questions about Biden's reelection as he entered the Capitol on Monday, but he told reporters: “As I've said before, I'm for Joe.”

The Senate's No. 2 Democrat, Illinois Sen. Dick Durbin, was more cautious.

“I watched the debate, it raised a lot of questions,” Durbin said. “He is trying to answer those questions. In some respects he's done it very effectively, in other respects not as effectively.”

One Democrat, Sen. Mark Warner of Virginia, had intended to gather senators Monday to discuss Biden privately, but a person familiar with his thinking said those conversations will take place in Tuesday's regular caucus luncheon with all Democratic senators.

“With so much at stake in the upcoming election, now is the time for conversations about the strongest path forward,” Warner said in a statement Monday.

Another Democrat, Sen. Alex Padilla of California, said it was “time to quit the hand-wringing and get back to door knocking.”

While some deep-pocketed donors may be showing discomfort, strategists working on House and Senate races said they have posted record fundraising as donors view congressional Democrats as a “firewall” and last line of defense against Trump.