U.S. President Joe Biden, in a letter to congressional Democrats, stood firm against calls for him to drop his candidacy and called for an "end" to the drama that has gripped the party after his dismal public debate performance two weeks ago.

Biden wrote in the two-page letter Monday that "the question of how to move forward has been well-aired for more than 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. "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."

The letter was sent from the campaign to Democratic lawmakers as they return to Washington following the July 4 recess.

Separately, Biden called into MSNBC's Morning Joe program to make his case for why he can once again beat Trump in a general election, as he did four years ago.

"I am not going anywhere," Biden told hosts Joe Scarborough and Mika Brzezinski.

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Congressional leaders tested

Biden was the consensus winner of two debates against Trump in 2020, but his performance two weeks ago — in which he struggled to finish sentences and couldn't counter Trump boasts — has seen an unclear number of Democratic lawmakers weighing whether Biden should stay in the race. A rare one-on-one interview the president sat for with ABC News late last week did not appear to assuage concerns.

Some deep-pocketed donors have also reportedly expressed discomfort, with Hollywood's Rob Reiner, who's regularly donated to Democratic candidates, saying he thinks Biden should step aside because "we lose our democracy" if Trump wins.

Biden, who turns 82 in November, appeared unmoved by such appeals on Monday morning.

"I'm getting so frustrated by the elites in the party who … know so much more," he said sarcastically.

The concern regarding Biden's cognitive abilities saw 15 top House committee members participate in a call on Sunday, and groups of the party's lawmakers are set to meet privately in person on Monday to address the subject. 

The upheaval also is testing the party's congressional leaders, headed by House Minority Leader Hakeem Jeffries and Senate Majority Leader Chuck Schumer. Both New Yorkers have refrained from publicly directing lawmakers on a path forward as they balance diverse opinions in their ranks.

Behind the scenes is Speaker Emerita Nancy Pelosi, who continues to field calls from lawmakers seeking advice about the situation and is widely viewed as the one to watch for any ultimate decision on Biden's future because of her proximity to the president and vote-counting skills in party politics.

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'Let Joe be Joe'

Time is not on the party's side, almost a month from the Democratic National Convention and just a week before Republicans gather in Milwaukee next week to renominate Trump as their presidential pick.

With respect to the Democratic affair in Chicago, Biden has already locked up nearly all of the pledged delegates, who cannot vote for other candidates unless he releases them.

Many Democrats are arguing the attention needs to be focused instead on the former president's felony conviction in the hush money case and pending federal charges in his effort to overturn the 2020 election.

Democratic Sen. Alex Padilla of California said it was "time to quit the hand-wringing and get back to door knocking."

Padilla spoke with Biden over the weekend, and urged his campaign to "let Joe be Joe."

"Given the debate, I think the campaign has no choice," Padilla said Sunday, explaining that Biden needs to hold town halls and unscripted events to show voters "the Joe Biden I know, and that most people in America have come to grow and love."

In addition to the lawmakers returning, the increased scrutiny comes as the president is set to host world leaders for a 75th anniversary NATO summit this week in Washington.