As questions continue to mount about President Biden's fitness for office, some House Republicans are privately concerned that replacing him at the top of the Democratic ticket could result in the GOP losing the White House in November.

"As a human, it's probably good for Joe Biden that he's now probably not going to have to be subjected to this another four years. But for the party, it's not great. It's not clear to me that it's good for us, either," one House Republican told Fox News Digital on the condition of anonymity.

"We had Trump versus Biden, which was a very lopsided, in my opinion, a very lopsided fight… the Dems would be insane to run Biden again. Like, they can't, it's like they can't at this point."

With a potentially younger and more popular replacement, the GOP lawmaker said it became "a tougher race."

"It changes everything. It's just a completely unknown wildcard right now," the GOP lawmaker said.

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They suggested that California Gov. Gavin Newsom or a similar popular figure somewhere like New York could inspire higher turnout among Democratic voters in those states, putting Republican-held swing seats in jeopardy in down-ballot races.

It comes after Biden's poor performance in Thursday night's CNN Presidential Debate, his first debate against former President Trump since 2020. 

The 81-year-old president spoke with a hoarse voice, reportedly due to a cold, and stumbled over his own answers several times during the primetime event. Viewers also observed him appearing tired and noticeably less sharp than he looked the last time he faced Trump.

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Even Biden's top allies in Congress conceded he had a bad showing. One House Democrat told Fox News Digital, "Obviously, there are conversations that I believe need to be had at all levels, with the realization of, this is not just about the presidency, this is about down-ballot."

Republicans have long contended that Biden is unfit for office. However, the new speculation among Democrats poses a political problem for the right – having to deal with the opponent they know, or being forced to weigh a completely different scenario less than six months before the election.

"I think both [scenarios] are risky," a second House Republican lawmaker told Fox News Digital. "We know what we know with Biden at the top… we don't know what we don't know with someone else."

A senior House GOP aide was more straightforward in their assessment, telling Fox News Digital point-blank that Biden running gives Republicans the best chance at victory.

"Virtually any Democrat that potentially replaces Biden has an exponentially better chance of defeating Trump. Biden staying at the top of the ticket is the best-case scenario for a Republican trifecta," the senior House GOP aide said.

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However, not everyone within the House GOP is concerned. Rep. Tim Burchett, R-Tenn., argued that voters will be focused on Biden's policies while in office, which the majority of Democrats support, but Republicans argue have hurt the country.

He said a new candidate would ultimately be distilled to a "shinier, cleaner version of Joe Biden."

"What are they gonna do different?" Burchett asked, speculating that voters would assume a new candidate would back "the same policies that got us into this mess."

Trump campaign spokesman Steven Cheung told Fox News Digital in response to House GOP concerns, "President Trump delivered the most dominant debate performance in history as Americans witnessed a clear contrast of proven America First policies versus Joe Biden's failed leadership at every turn…Democrats and their media enablers have created this problem by turning a blind eye to Biden's clear cognitive and physical decline for the last four years. Now they have to face the reckoning of having an inept candidate as their nominee."

A new CBS News and YouGov poll released over the weekend showed nearly three quarters of Democratic voters believe Biden does not have the cognitive health to serve as president. 

Despite the fallout from his debate performance, however, Biden has shown no intention of stepping aside, and top Democratic allies have publicly coalesced around his decision.

Biden's campaign did not respond to a request for comment by the time of publication.