A Democratic senator became the first in Congress's upper chamber to call on President Biden to exit the 2024 race on Wednesday night, and left the question of Biden's successor open-ended. 

"We cannot unsee President Biden’s disastrous debate performance. We cannot ignore or dismiss the valid questions raised since that night," Sen. Peter Welch, D-Vt., wrote in an op-ed for the Washington Post on Wednesday, which was published shortly after the Senate adjourned for the evening.

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Peter Welch, Joe Biden

Sen. Welch was the first Democrat senator to call on Biden to drop out of the race.  (Getty Images)

Only one day earlier, Welch didn't answer a question from Fox News Digital about whether he wanted Biden to be the party's nominee. "He's our nominee," he said. 

In his essay, Welch heaped praise onto Biden and his presidency. "But I, like folks across the country, am worried about November’s election," he added. 

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Joe Biden

President Biden shocked the nation with his disastrous debate performance, sparking calls for him to step out of the 2024 race. (Getty Images)

"For the good of the country, I’m calling on President Biden to withdraw from the race," the senator wrote. 

He urged Biden to "reassess whether he is the best candidate" to beat former President Trump. 

"In my view, he is not," Welch said. 

For a replacement, Welch said Vice President Kamala Harris is "a capable, proven leader," but stopped short of endorsing her alone. He added, "we have other electable, young, energizing Democratic governors and senators in swing states."

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Joe Biden, Donald Trump

President Biden, left, and former President Donald Trump, right. (Getty Images)

Welch laid out all the problems he sees with Trump's candidacy in the op-ed, but noted, "the national conversation is focused on President Biden’s age and capacity" instead.  

"Only he can change it," the Democrat said of Biden. 

The Vermont senator cited "real concerns of regular voters who I’ve heard from recently" about Biden, explaining that they "are worried that he can’t win this time, and they’re terrified of another Trump presidency."

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Kamala Harris

Harris is a potential successor to Biden if he exits the race.  (Bizuayehu Tesfaye)

"These new shifts — in Minnesota, New Hampshire, Nevada, Arizona and Georgia — must be taken seriously, not denied or ignored," Welch warned of the new polls coming out of previously safe states for Democrats. 

Welch ended the essay by once again pleading with Biden "to put us first, as he has done before. I urge him to do it now."

While the Vermont Democrat is the first in his caucus to make the request of Biden, he isn't the only one making his concern known. On Tuesday, Sen. Michael Bennet, D-Colo., shared that he told his colleagues during a caucus meeting that he didn't believe Biden could beat Trump in an appearance on CNN. 

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The Senate Democrats discussed Biden and his candidacy during their regularly scheduled caucus meeting on Tuesday, where Bennet said he made his worry known. 

Democratic senators will also be headed to the Democratic Senatorial Campaign Committee (DSCC) on Thursday afternoon for a special meeting with top Biden campaign advisers. 

Senior Biden advisers Mike Donilon and Steve Ricchetti, and campaign chair Jen O'Malley Dillon will join the senators, a source familiar confirmed to Fox News Digital.