Former Democratic Missouri Sen. and MSNBC political analyst Claire McCaskill admitted that President Biden "failed" during Thursday's debate to prove he’s fit enough for another term in office.

The pundit stressed that Biden’s "one job" going into the debate was to prove his age wasn’t a hindrance to his leadership and that he completely missed the mark. She also lamented having to make the claim because of her longtime support for the president.

"I’m not the only one whose heart is breaking right now," McCaskill said about the wide swath of voters and other pundits who acknowledged Biden’s uneven debate performance against former President Trump.

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McCaskill on MSNBC

MSNBC analyst Claire McCaskill criticized President Biden's debate performance Thursday night.  (Screenshot/MSNBC)

McCaskill gave her assessment on Biden’s performance during MSNBC’s post-debate analysis Thursday night. She began by telling network host Rachel Maddow the "easy part," which she said is that Trump "is a liar, a flawed character, mean, a jerk, very unlikable, and that was obvious tonight."

"And now the hard and heartbreaking part," she continued, pivoting to Biden's debate showing.

"My job now is to be really honest," she said. "Joe Biden had one thing he had to do tonight and he didn't do it. He had one thing he had to accomplish, and that was reassure America that he was up to the job at his age, and he failed at that tonight."

The former lawmaker didn't speculate whether Biden's performance will cause him to be booted off the presidential ticket. 

"I don’t know that," she said after mentioning that Democrat lawmakers and political strategists have been contacting her about rumors that Biden will be replaced.

"I think we’ll know a lot more in a few weeks how this plays out, how the polling plays out."

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Biden CNN debate

President Joe Biden participates in the CNN Presidential Debate at CNN Studios on June 27, 2024 in Atlanta, Georgia. President Biden and Republican presidential candidate former President Donald Trump faced off in the first presidential debate of the 2024 campaign. (Andrew Harnik/Getty Images)

McCaskill then restated how sad seeing Biden’s decline is for her and other Biden supporters throughout the country.

"There's a lot of people who watched this tonight and felt terribly for Joe Biden," she said. "And you know, you have to ask, how did we get here?"

"How did we get to the point that we’re spending a whole lot of time talking about the vice president tonight instead of talking about the president?" she asked.

"I don't know how the rest of the story is written," McCaskill continued. "I don't know if things can be done to fix this. They might, and Trump is so terrible that this might heal itself, but based on what I'm hearing from a lot of people — and some of them are people that are in high elected offices in this country, and you might guess where they serve — there is a lot more than hand wringing tonight."

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McCaskill also provided a tip for the president’s advisers to have a "heart-to-heart" with Biden "about his ability to exude strength," and concluded by asking why the Democratic Party has not freed up space for Gov. Gavin Newsom, D-Calif., and Vice President Kamala Harris to run as a presidential ticket.

"How come the Democratic Party doesn’t have them at the top of the ticket instead of using them to shore up what have become, after tonight, some glaring weaknesses in our president?"