Democrats are talking about replacing Joe Biden. That won't be so easy.

President Joe Biden's performance in the first debate Thursday has sparked a new round of criticism from Democrats, as well as public and private musing about whether he should remain at the top of the ticket.

"There is a sense of shock at how he came out at the beginning of this debate. How his voice sounded. He seemed a little disoriented," David Axelrod, who served as a top White House and campaign official for former President Barack Obama, said on CNN.

"There are going to be discussions about whether he should continue," Axelrod added.

One Democratic lawmaker, asked by NBC News whether the debate inspired confidence in Biden, replied: "The best thing I can do to help Joe Biden is to pretend I didn’t get your text."

Publicly, Democratic officials continue to largely rally around Biden, and argue a lackluster performance doesn’t change the fundamental stakes of the election.

California Gov. Gavin Newsom, whose name is often floated as a potential alternative nominee, told reporters in the "spin room" after the debate that his party "could not be more wholly unified behind Biden" and said the president should not step aside.

But the private whispers whipped up after Thursday’s debate performance, during which Biden had a raspy voice, spoke softly and a times seemed to lose his train of thought, leading his aides to try to deflect mid-way through the debate by saying he had a cold.

In the modern era, a national party has never attempted to adversarially replace their nominee, in part, because they know it would likely fail. The issue came before both parties in 2016, but neither took action.

Party rules make it almost impossible to replace a nominee without their consent, let alone smoothly replace them with someone