Dems who were pressed to retire due to age concerns have a history of refusing to go

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As calls for President Joe Biden to retire have increased in the Democratic Party following Thursday night's presidential debate against former President Donald Trump, replacing him could prove to be an uphill legal hurdle, albeit one that some political groups are already preparing for. Biden's troubles come amid a recent series of progressive figures in Congress and the courts who have refused to retire despite pressure from liberal activists.

"The leverage is pretty much all with President Biden," Mike Howell, executive director of the Heritage Oversight Project – a conservative watchdog group – told Fox News Digital in an interview.

"It is much more difficult to forcefully replace him than it would be for him to voluntarily withdraw, and so I expect that is the nature of the conversations. I think the only people right now that are fighting to keep President Biden on the ballot are President Biden, Jill Biden and, interestingly enough, me, because we will sue to make sure his name stays on the ballot."

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Howell added it's "not easy" to fill a replacement for a presidential candidate, which would create a "massive legal and logistical nightmare for the replacement candidate."

"There are precedents of candidates dying and other state and local races before, but this is unchartered