On Monday, Biden sent a letter to Democratic lawmakers saying he is “firmly committed to staying in this race” and calling for an “end” to speculation within the party about the future of his candidacy.

Here is a look at the 21 known congressional Democrats -- 20 in the House, one in the Senate -- who have said either publicly or privately they’d like to see Biden step aside.

Rep. Earl Blumenauer

The Oregon lawmaker, who is retiring in January, on Wednesday joined the chorus of Democrats urging Biden to withdraw. 

“It is a painful and difficult conclusion but there is no question in my mind that we will all be better served if the president steps aside as the Democratic nominee and manages a transition under his terms,” Blumenauer said. “He has earned that right.”

Rep. Ed Case

Case, a longtime fixture in Hawaii politics, said in a statement Thursday that his "guidepost is what is the best way forward for our country."

"I do not believe President Biden should continue his candidacy for re-election as President," Case said, adding that his decision has nothing to do with the incumbent's "character and record" as president. "If it did, there would be no decision to make."

Rep. Angie Craig

The Minnesota congresswoman issued a statement Saturday saying she has “great respect for President Biden’s decades of service to our nation and his steadfast commitment to making our country a better place,” but, “given what I saw and heard from the President during last week’s debate in Atlanta, coupled with the lack of a forceful response from the President himself following that debate, I do not believe that the President can effectively campaign and win against Donald Trump.”

Craig called for “an open, fair, and transparent Democratic process to select a new nominee to inspire and unite our great nation.”

“If we truly believe that Donald Trump and MAGA Republicans must be stopped, there is only a small window left to make sure we have a candidate best equipped to make the case and win,” she said.

Rep. Lloyd Doggett

On July 2, the Texas lawmaker became the first congressional Democrat to urge Biden to drop out the race, citing his performance in the presidential debate and the need to defeat former President Donald Trump, the presumptive Republican nominee. 

“Instead of reassuring voters [during the debate], the President failed to effectively defend his many accomplishments and expose Trump’s many lies,” Doggett said in a statement.

“Our overriding consideration must be who has the best hope of saving our democracy from an authoritarian takeover by a criminal and his gang,” he continued. “Too much is at stake to risk a Trump victory.”  

In an interview with Spectrum News after his announcement, Doggett said that he came to the decision to ask Biden to withdraw "reluctantly and sadly" because of his accomplishments as president.

"I've watched the polls and what's happened over the last year," he said. "We've been running behind, hoping that we get some momentum out of this debate. Instead, we got disappointment."

"I watched it with my wife, we were alarmed by his inability to counter the Trump lies and to really defend an admirable effort that the president's made these last few years," he continued, detailing that he discussed his position about wanting to replace Biden as the nominee with colleagues in Congress and his constituents in Texas.

He also said the Supreme Court's ruling in Trump's immunity case last week underscored the importance of defeating the Republican ex-president at the ballot box in November.

"There is so much at risk in having a criminal and his gang take over our government, that I just think we have to have a stronger candidate than President Biden has happened to be," Doggett added.

Rep. Raúl Grijalva

Grijalva, a progressive Democrat from Arizona, was the second member of Congress to call on Biden to step aside, telling The New York Times on July 3: “What he needs to do is shoulder the responsibility for keeping that seat — and part of that responsibility is to get out of this race.”

Grijalva said a second Trump presidency would be “very, very dangerous,” describing the former president as an “anti-democratic, authoritarian despot.”

Rep. Jim Himes

The Connecticut lawmaker was one of at least four House Democrats who said during a private call Sunday that Biden should step aside. Himes is the top Democrat on the Intelligence Committee.

According to Politico, Himes said he has received several hundred texts and emails about Biden’s age, all from people who wanted the president to leave the race. Himes also reportedly expressed concerns about Democrats losing both chambers of Congress if Biden presses on.

On Thursday, after Biden's NATO press conference, Himes went public with his call for Biden to exit the race.

"Joe Biden’s record of public service is unrivaled. His accomplishments are immense. His legacy as a great president is secure," Himes wrote on X, the platform formerly known as Twitter. "He must not risk that legacy, those accomplishments and American democracy to soldier on in the face of the horrors promised by Donald Trump."

Rep. Mike Levin

Almost two years ago, with the midterms rapidly approaching, Biden campaigned alongside Levin in San Diego as the California Democrat sought reelection. 

On Friday, Levin called for Biden to step aside from the Democratic ticket.

"Like so many of you, I was naturally concerned about President Biden’s performance in the recent debate," Levin said in a statement to Spectrum News. “Since then, I’ve made my opinions known in the appropriate manner with House Democratic leadership and my colleagues. And I called upon all Americans to give the President a window to make an expeditious decision about his candidacy."

After calling Biden "an outstanding leader" and hailing his decades of service to the country, Levin said he believes "the time has come for President Biden to pass the torch."

"We must prevail against the incalculable threat Donald Trump poses to the American institutions of freedom and democracy," he said. "Donald Trump actively seeks a bleak authoritarianism and the overthrow of the values which have guided us towards justice and prosperity for nearly two and a half centuries. “Once again, our national mettle must be forged in the crucible of history.  It is time to move forward.  With a new leader. Together.”

According to POLITICO, Levin was part of a meeting with Biden and his fellow members of the Congressional Hispanic Caucus shortly before putting out his statement.

Rep. Seth Moulton

Moulton, of Massachusetts, told radio station WBUR on July 4 that he does not believe Biden can defeat Trump and should bow out.

“President Biden has done enormous service to our country, but now is the time for him to follow in one of our Founding Fathers — George Washington’s — footsteps and step aside to let new leaders rise up and run against Donald Trump,” Moulton said.

On Sunday, Moulton told WCVB-TV: “There are a lot of colleagues who share my concern, but have not gone public. We should be cleaning up and down the ballot, and that's just not the case right now. So, we need to ask, 'What do we need to do differently?’”

Rep. Jerry Nadler

The New York Democrat and ranking member of the Judiciary Committee was on the same call Sunday with Himes. 

Nadler, as one of the more senior members on the call, was the first person to say that Biden should step aside, according a person familiar with the call who was granted anonymity to discuss it with The Associated Press. He did so aware of his seniority and that it would allow others to join him.

However, on Tuesday Nadler told CNN of Biden: “He said he’s going to remain in, he’s our candidate, and we’re going to support him."

Rep. Scott Peters

Shortly after Himes' post-debate detraction, Peters, a California Democrat, expressed that in a "high stakes" election, Democrats "are on a losing course" with Biden at the helm.

While praising his accomplishments as president, Peters said in a statement that Biden's debate performance "was not a blip."

“Today I ask President Biden to withdraw from the presidential campaign," Peters said. "The stakes are high, and we are on a losing course. My conscience requires me to speak up and put loyalty to the country and to democracy ahead of my great affection for, and loyalty to, the President and those around him."

Rep. Brittany Pettersen

On Friday, the day after Biden's NATO press conference, Pettersen, a Colorado Democrat, urged Biden to "please pass the torch" to a new generation of Democratic leaders in a statement posted to social media.

Pettersen, an organizer for the incumbent Democrat's 2008 campaign, expressed "deep admiration for Joe Biden and all he has done for this country," which she said makes her decision to ask him to stand aside "more painful."

"Please pass the torch to one of our many capable Democratic leaders so we have the best chance to defeat Donald Trump," she added.

Rep. Mike Quigley

In an appearance on MSNBC’s “All In With Chris Hayes” on Friday, Quigley, of Illinois, had a direct message for Biden: “Your legacy is set. We owe you the greatest debt of gratitude, the only thing you can do now to cement that for all time and prevent utter catastrophe is to step down and let someone else do this.”

Quigley doubled down on his opinion Monday, saying Biden’s Friday interview with ABC News did nothing to change his mind. 

“He looks very frail,” Quigley told CNN. “His voice is very soft. It’s not robust. And again, it is not how I perceive that. It’s how the American people perceive it.”

Rep. Pat Ryan

A Democrat representing a frontline New York district, Ryan called on Biden to step aside Wednesday, telling The New York Times, "I’d be doing a grave disservice if I said he was the best candidate to serve this fall."

"For the good of our country, for my two young kids, I’m asking Joe Biden to step aside in the upcoming election and deliver on the promise to be a bridge to a new generation of leaders," Ryan told the outlet. "I really hope, with all my heart, that he will listen."

In a subsequent post on X, formerly known as Twitter, Ryan doubled down on his comments.

"Trump is an existential threat to American democracy; it is our duty to put forward the strongest candidate against him," he wrote. "Joe Biden is a patriot but is no longer the best candidate to defeat Trump."

In an interview with Spectrum News on Thursday, Ryan called the debate "a wake-up call" for Democrats.

Trump “is unfit for office and has to be stopped, he cannot go anywhere near the White House again. And so I believe it's our patriotic duty as a party to put forward the strongest candidate to defeat him," he added.

Rep. Brad Schneider

Schneider, an Illinois Democrat and prominent member of the New Democrat Coalition in the House, said in a statement Thursday that "the time has come ... for President Biden to heroically pass the torch to a new generation of leadership to guide us to the future he has enabled and empowered us to pursue." 

Schneider hailed Biden's accomplishments in office, notably leading the country through the COVID-19 pandemic and the subsequent economic recovery in its aftermath, and said that the incumbent "now has the opportunity to secure his legacy and boldly deliver the nation to a new generation of leadership."

"The stakes in this election could not be higher," he said. "Donald Trump and the administration he would install are an absolute threat to the very core of our nation."

Rep. Hillary Scholten

Scholten, who represents a district in western Michigan once held by Gerald Ford, joined the chorus calling for Biden to step aside Thursday, hailing his "incredible" legacy but expressing concern that Americans cannot "unsee" his performance at last week's debate.

"We just have too much at stake in this election to sit on the sidelines and be silent while we still have time to do something," Scholten, a frontline Democrat in a battleground state, said in an interview with The Detroit News on Thursday.

She said she will continue to support Biden over Trump should she stay in the race but urged him to "allow a new leader to step up."

"But the people of Michigan’s 3rd Congressional District elected me to represent them with integrity," Scholten said. "They elected a Congresswoman they trust to speak the truth, even when it’s hard. They voted for someone who would put America's future first and stand up for what is right. That's what I am doing now."

Rep. Mikie Sherrill

The New Jersey congresswoman said in a statement Tuesday she is asking Biden to “declare that he won’t run for reelection and will help lead us through a process toward a new nominee.”

Sherrill praised Biden for his more than 50 years serving the country and working to pass “remarkable legislation that will reverberate for generations.” She said her constituents “want a leader who can continue to build on our successes but is also able to turn the nation’s attention to the urgent threat that Trump presents to our democracy, to our freedoms, to our country.”

The “stakes are too high — and the threat is too real — to stay silent,” Sherrill said.

Rep. Adam Smith

On Monday, Smith, the top Democrat on the House Armed Services Committee, urged Biden to "take a step back" from the ticket and called for Vice President Kamala Harris to take his place.

"I think it’s become clear that he’s not the best person to carry the Democratic message," the Washington state Democrat said on CNN, before praising the Democrats' platform and record and acknowledging Biden's role in the country's economic recovery from the COVID-19 pandemic.

He went on to call a second Trump presidency a "complete disaster," condenming the far-right Project 2025 agenda, which the ex-president attempted to distance himself from last week, and his economic proposals.

"We've got a good message," said Smith, who also made his opinion known at Sunday's call of top Democratic committee members. "The president has shown he is not capable of delivering that message in an effective way."

Rep. Eric Sorensen

The Illinois Democrat became the third Democratic lawmaker following Biden's NATO press conference to call for his departure from the race.

“In 2020, Joe Biden ran for President with the purpose of putting country over party," Sorensen said in a statement posted to social media. "Today, I am asking him to do that again.”

Rep. Greg Stanton

Arizona's Stanton, who called himself "one of President Biden's earliest supporters in 2020" in a statement Thursday, hailed the president's record in delivering for his state, but argued that Trump "poses an existential threat" to the U.S. Constitution and American democracy and the party needs a nominee who can make a case against him.

"For the sake of American democracy ... I believe it is time for the President to step aside as our nominee," he said.

"The stakes in this election could not be higher," he wrote in a post on X, formerly Twitter. "For our country's sake, it is time for the President to pass the torch to a new generation of leaders.

Rep. Mark Takano

The California lawmaker, too, said during Sunday’s private call that Biden should withdraw, a source told the AP. Takano is the ranking member of the the House Veterans’ Affairs Committee.

Many others on the call raised concerns about Biden’s capability and chance of winning reelection, even if they stopped short of saying Biden should step out of the race.

Sen. Peter Welch

The Vermont politician on Wednesday became the first Senate Democrat to call for Biden to leave the race.

"I understand why President Biden wants to run," Welch said in an opinion piece in The Washington Post. "He saved us from Donald Trump once and wants to do it again. But he needs to reassess whether he is the best candidate to do so. In my view, he is not. For the good of the country, I’m calling on President Biden to withdraw from the race."

Welch cited recent polling analysis from the Cook Political Report that found that six battleground states have shifted toward Trump after Biden’s disastrous debate performance. Some states, like Minnesota and New Hampshire, are still expected to lean Democratic, while Nevada, Arizona and Georgia have moved from "toss up" to "lean Republican."

Spectrum News' Kevin Frey and The Associated Press contributed to this report