Republican Sen. Bill Cassidy described the case against former President Donald Trump for allegedly mishandling classified documents as "almost a slam dunk" and said he thinks Trump should drop out of the 2024 presidential race.

"I mean, you're just asking me my opinion. But he will lose to Joe Biden, if you look at the current polls," he told CNN's Kasie Hunt on "State of the Union."

"I think any Republican on that stage in Milwaukee will do a better job than Joe Biden. And so I want one of them to win. If former President Trump ends up getting the nomination, but cannot win a general, that means we will have four more years of policies which have led to very high inflation ... and to many other things which I think have been deleterious to our country's future," the Louisiana senator said.

The comments from Cassidy, who was one of seven GOP senators who voted to convict Trump in 2021 at his second impeachment trial, mark some of his strongest criticism of Trump to date. They come as the various charges against Trump continue to dominate the GOP primary, with the former president widely viewed as the party's front-runner.

Trump has been indicted by a federal grand jury in the special counsel's investigation into the aftermath of the 2020 election and on dozens of federal counts related to the special counsel investigation into mishandling of classified documents. He also faces charges in Georgia over efforts to overturn Biden's 2020 victory in the state, and in New York, where he is accused of falsifying business records related to his role in a hush-money payment scheme involving adult film actress Stormy Daniels.

Trump has denied all wrongdoing and deemed many of the cases politically motivated.

Of the 91 charges against Trump in the four different criminal cases spanning four different jurisdictions, Cassidy called those related to mishandling classified documents "almost a slam dunk." He mentioned the recording of the 2021 meeting in Bedminster, New Jersey, where Trump discussed holding secret documents he had not declassified. "If it's proven, we may have a candidate for president who's been convicted of a crime," Cassidy said.

He added that President Joe Biden "needs to be replaced, but I don't think Americans would vote for someone who's been convicted."

Cassidy previously told CNN that he didn't think Trump would be able to win a general election, pointing to the GOP's disappointing performance in last year's midterm elections, when several candidates endorsed by the former president were defeated.

When pressed on whether he would vote for Trump should he become the GOP nominee, Cassidy demurred.

"I'm going to vote for a Republican," Cassidy said.