Washington — President Biden on Monday sent a letter to congressional Democrats saying that he is "firmly committed" to staying in the race and making clear that he wouldn't be running again if he "did not absolutely believe I was the best person to beat Donald Trump in 2024."

Lawmakers are returning to Washington this week after a July 4 recess, which came as questions about Mr. Biden's ability to serve another term roiled the political sphere following a disastrous debate performance last month. A slow leak of Democratic lawmakers have since called on Mr. Biden to step aside from the race. But the president has been clear that he will not drop out. 

In the letter, the president cited the votes he received in the primaries so far, saying "the voters of the Democratic Party have voted," and selected him as their presumptive nominee. 

Mr. Biden said the question of "how to move forward" had been aired for more than a week, saying it's "time for it to end."

"We have 42 days to the Democratic Convention and 119 days to the general election," he said. "Any weakening of resolve or lack of clarity about the task ahead only helps Trump and hurts us." 

The president has been working to assuage concerns about his ability to serve another term with a number of appearances in recent days. And at every turn, he's made clear his intention to stay in the race — from a highly anticipated interview with ABC News anchor George Stephanopoulos on Friday to rallies in Wisconsin and Pennsylvania over the holiday weekend. 

Mr. Biden has also made outreach efforts, with a campaign official saying he personally made 20 calls to congressional members since the debate. Additional calls are expected. 

But it's unclear whether the efforts to quell concerns among the party will be successful. Attention will be especially this week paid to Mr. Biden's support in the Senate, where he represented Delaware for more than three decades. No Senate Democrats have publicly called for the president to step aside. And Sen. Mark Warner of Virginia scrapped a Monday meeting with a group of Senate Democrats to discuss the president's bid, a source familiar with the senator's thinking confirmed to CBS News. 

Ed O'Keefe, Nikole Killion, Scott MacFarlane and Fin Gómez contributed reporting.

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