Morning Joe host Joe Scarborough clashed with former Missouri senator and MSNBC contributor Claire McCaskill over the stakes of Thursday's Democratic debate, accusing McCaskill of shoveling "B.S. around on our set" by downplaying the significance of the debate for current frontrunner Joe Biden.

"Every Democrat I know that is desperate for Donald Trump to be beaten is worried about Joe Biden," Scarborough said. "Worried that Joe Biden's not up to it, worried that Joe Biden is too old, worried that Joe Biden commits too many gaffes, worried this, worried that. It's all you hear."

He then previewed the debate as a showdown between Biden and the surging Sen. Elizabeth Warren (D., Mass.), who Scarborough said is a polarizing candidate within the Democratic Party.

"Right now the overriding fear is Joe Biden is not up to the task of running for president, and for weeks people have been talking about this third debate," Scarborough continued. "It is critical that Joe Biden hits his marks and that he doesn't just sort of trail off on answers and say, ‘My time's run out.'"

"Claire, are we overstating the importance of this debate to Joe Biden?" he asked.

"Yeah, kind of," McCaskill responded. "And I think you're overstating how worried everybody is too, frankly, Joe."

"No, I'm not. No, no, no, Claire, listen, I know you were a highly respected person in the Democratic Party, but we can't let you, like, shovel B.S. around on our set, because everybody's saying it," Scarborough said.

"First of all, just as many people are saying that they're worried about a nominee that's too left. I'm not saying there's no conversation about it Joe, I think you overstated it," McCaskill pushed back.

"Here's the thing. Joe Biden has withstood a media narrative that from day one was: ‘He's old, he's a gaffe machine, he's yesterday's news, he can't get anything right.' This has been the media narrative on him," McCaskill said. "And frankly it has been a blanket on him from the day he started. His polling numbers, surprisingly, have held up very well."

McCaskill also defended Biden's gaffes as functions not of Biden's age, but of "Joe Biden being Joe Biden," which she says voters find appealing.

"Frankly there's just as much pressure on Elizabeth Warren as there is on Joe Biden."