(NewsNation) — Rep. Mike Quigley, D-Ill., says President Joe Biden needs to leave the race.

“As president on his worst day, he’s 10 times better than Trump. But as a candidate, that’s just not the case,” Quigley said during an appearance on “CUOMO.” “It’s odd, but it’s two different things. We haven’t had a good day since the debate.”

Quigley praised Biden’s legacy of public service but said his call for the president to step down is “not about loyalty.”

Biden has remained adamant about running for reelection, but calls for him to step aside have been growing.

“This is one of the most important arguments we can make,” Quigley added. “I think whatever action we take has to happen now for this to work at all.”

The Biden campaign went into crisis mode following the debate, attempting to shore up support from top Democrats in Congress and Democratic governors. Some, including Vice President Kamala Harris, have remained vocal in their support for the president.

Earlier Monday, Biden said in a letter sent to Democratic lawmakers that he’s “firmly committed” to running in the 2024 election.

Writing in the letter that he’s had “extensive conversations” with party leadership, elected officials and voters over the past 10 days, Biden added they have “good faith fears and worries” about what is at stake in this election.

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“Believe me, I know better than anyone the responsibility and the burden the nominee of our party carries,” Biden wrote.

However, “the question of how to move forward has been well-aired for over a week now,” Biden wrote. “And it’s time for it to end.”

Biden has fielded questions over whether he should be the Democratic nominee for president following his highly criticized performance at the first presidential debate two weeks ago. As he debated presumptive Republican nominee and former President Donald Trump, Biden stumbled through his words and appeared at times to be confused. Although Trump made multiple false statements during the debate, concerns over Biden’s age and mental fitness took center stage.

To Democrats in Congress, though, Biden wrote: “I wouldn’t be running again if I did not absolutely believe I was the best person to beat Donald Trump in 2024.”

“We have a historic record of success to run on,” Biden wrote.

NewsNation’s Steph Whiteside and Kellie Meyer contributed to this report.