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A growing number of Republican lawmakers don't think President Biden has gone far enough in abruptly calling off his presidential campaign and want him to resign immediately; a move experts believe is both unlikely and part of a political strategy to hold Harris accountable for what they say is complicity in Biden's alleged declining mental acuity.

"There are reasons for them to want her to take over the presidency or him to step down that are beyond just the fact that he's 'not in the greatest shape,'" presidential historian and former Secretary of Health and Human Services Tevi Troy told Fox News Digital in an interview. 

"For example, if she takes over the presidency, she has less time to campaign," said Troy, who is also a senior fellow at the Bipartisan Policy Center. "Second of all, she has to go out there and answer questions, which she isn't so great at. Third of all, there's more and more questions about, well, ‘Did you know that Biden was seriously diminished when you were vice president?’ And that's a potential scandal."

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President Joe Biden and Vice President Kamala Harris hold hands on balcony

President Biden and Vice President Harris (Tierney L. Cross)

Meanwhile, GOP lawmakers who have been calling for Biden's resignation for months have re-upped their request. Sen. Rick Scott, R-Fla., told Fox News Digital on Monday that he's unsure "politically" how it may play out if Harris assumes the presidency, "but we've got to have a president that can make a logical decision," he said.

"He clearly can't do it, and he acknowledged it by not running, that he's not up to it, and so I don't see why he would [remain as president]," Scott said. 

Scott falls in line with several Congressional Republicans who have called on Biden to immediately resign since Sunday. House Speaker Mike Johnson, R-La., who is leading the GOP in calling for Biden's resignation, said in a statement, "If Joe Biden is not fit to run for President, he is not fit to serve as President. He must resign the office immediately. November 5 cannot arrive soon enough."

House GOP Conference Chair Elise Stefanik, R-N.Y., similarly said, "If Joe Biden can’t run for re-election, he is unable and unfit to serve as President of the United States. He must immediately resign. The Democrat Party is in absolute free fall for their blatantly corrupt and desperate attempt to cover up the fact that Joe Biden is unfit for office."

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Trump and Kamala Harris split image

Former President Trump and Vice President Harris (Getty Images)

According to one House Republican strategist, aside from the growing calls for Biden to resign, all the offensive campaign efforts will be directed toward Harris as she inches closer to securing the DNC nomination in August and Democrat endorsements pour in.

"We're not really seeing anyone seriously put up a challenge," the strategist said. "We saw [Sen.] Joe Manchin say he's not interested. So, I think it's very important for us to quickly pivot and go after Kamala and define her as not only being responsible for every terrible policy that you see come out of the Biden administration, whether that's [the] border, the uptick in crime, the cost of living crisis, but we also have to go back and look at her policy record from prior to the Biden administration."

When asked about a potential Harris presidency if Biden resigns, the strategist said "that's not in the realm of possibilities."

"I don't think Democrats are ever going to actually force Joe Biden out," the strategist said.

Biden has not been seen publicly since a letter on his X account was released announcing the suspension of his presidential bid on Sunday. Biden began to self-isolate last week after contracting COVID-19.

Meanwhile, Harris – who got Biden's endorsement on Sunday – has raised nearly $50 million in grassroots donations since President Biden suspended his re-election bid and gave remarks Monday at a NCAA event.

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President Biden

President Biden (Hannah Beier/Bloomberg via Getty Images)

The unprecedented announcement came as an increasing number of Democrat lawmakers had begun to publicly call for Biden to step aside, and the party's leadership reportedly was engaged in efforts to convince Biden, 81, he could not win in November's general election against former President Trump, the 2024 GOP nominee who Biden defeated four years ago to win the White House.

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Biden quickly offered his "full support and endorsement" for Harris to take over as the party's presidential nominee.

"It has been the greatest honor of my life to serve as your president," Biden wrote in a public letter. "While it has been my intention to seek reelection, I believe it is in the best interests of my party and the country for me to stand down and focus solely on fulfilling my duties as president for the remainder of my term."

Biden began facing questions about his mental acuity after multiple bombshell reports revealed many lawmakers on the Hill had expressed concerns about the president behind closed doors. Then a disastrous debate performance against Trump last month caused a flurry of questions from the media, which was paired with subpar polling numbers. 

Fox News Digital's Brooke Singman and Elizabeth Elkind contributed to this report.