Marco Rubio warned Monday that there will be a "reckoning" in the conservative movement for those backing Donald Trump.

Speaking with radio host Mike Gallagher, Rubio frankly criticized the Republican frontrunner and the voters who "fell into" supporting him. Here is a partial transcript:

There is going to be a reckoning here. I don't know if it's going to happen before this election or after this election, but there's going to come a moment where people in the conservative movement who are supporting Donald Trump are going to stop and say, My God, what have we done? What have we done? There's going to be prominent people out there that are going to spend a significant amount of time over the next few years explaining away how they fell into this over the last few months. Because Donald Trump, by no standard, is he a conservative. By no other measure can you argue that he is a serious presidential candidate. This is a man who has refused to offer a serious solution on any major issue, and to the extent he has, it's crazy policies that would harm the country.

The Florida senator also said that if Trump is the GOP nominee, "we are going to lose this election." He predicted the same media that built him up will eventually "tear him to shreds" and hand Hillary Clinton a general election victory.

Asked if all of this candid talk meant that he ultimately might not back Trump, Rubio said he didn't even want to think about it at the moment.

"It's harder and harder to justify it because it continues to get worse and worse," he said.

Rubio also had an ominous assessment of the country's uncivil tone:

I have a 15-year record of standing strong on conservative principles. But I think you can be a strong and passionate conservative, and yet engage in a civilized and respectful debate about the issues before our country, because I believe our republic is worth preserving. And if we reach a point in this country where people cannot have a debate about public policy without punching each other in the face or hating each other, we got a big, big problem. And that's where we're headed. We are now a country where everyone is starting to hate each other. What kind of country is that? That's not the country I want my kids to inherit. And when you have leaders that are encouraging us to move in that direction, we've got a big problem.

Rubio predicted he would win the Florida primary Tuesday, though he trails by 19 percentage points in the RealClearPolitics average of polls.