Former defense secretary Mark Esper on Wednesday sharply criticized his old boss Donald Trump after the ex-president announced his 2024 presidential bid.

"I think he's unfit for office," Esper, who served under the Trump administration from 2019 to 2020, said of Trump on CNN. 

At his Mar-a-Lago club on Tuesday evening, Trump announced to a crowd of supporters that he's launching a third campaign for the White House. His remarks, which lasted more than an hour, "were very subdued and uninspiring," according to Esper.

"I think it's time for the Republican party, and frankly both parties, to move on to a next generation of leaders," he added. 

Republicans have been publicly rebuking Trump after the party underperformed in the midterm elections, blaming the disappointing results on the former president because many of his endorsed candidates lost in key races, including Pennsylvania, Arizona and Nevada.

Esper echoed that sentiment on Wednesday, telling CNN, "The election last week was an example of Donald Trump is incapable of winning elections."

The party lost the Senate and only narrowly won the House Votes are still being counted in less than a dozen races.

"He's done more to help the Democrats than he has Republicans," Esper said of Trump. "And there's no reason why we shouldn't have a bigger margin in the House and we should've taken the Senate, and yet we haven't."

Trump has not yet received prominent endorsements for his 2024 bid other than from loyalists like GOP Reps. Marjorie Taylor Greene of Georgia and Elise Stefanik of New York. Republicans in recent days have increasingly pointed to other leaders across the country, like Florida Gov. Ron DeSantis, as examples of who can move the party forward. DeSantis handily won his reelection last week.

DeSantis "appears to me to be the frontrunner" for the 2024 Republican nomination, Esper told CNN.



"I think if you want to govern, if you want to govern consistent with conservative principles, then you have to win elections," he said. "And Donald Trump can't win elections."