Are we seeing a new Donald Trump after Clinto...

MSNBC host Joe Scarborough on Wednesday said he won't support Donald Trump for president until he proves he's not a bigot.

"Donald, guess what, I'm not going to support you until you get your act together. You're acting like a Bush-league loser, you're acting like a racist, you're acting like a bigot," the host of "Morning Joe" said.

Scarborough, a former GOP congressman from Florida, said that Trump should apologize for his "racist" comments and called on Republicans to withhold their Trump endorsements and stand up against him. The two used to have a much friendlier relationship.

Get Breaking News Delivered to Your Inbox

"I have taken the gun away from my head I am putting it on the table and now. It is in your hands on whether you are going to prove to the Republican party and me personally that you're not a bigot," he said.

"Don't use Hillary Clinton as a threat against me, don't use Hillary Clinton as an excuse, as your blank check to say racist things about people born in Indiana," Scarborough added. "No, Donald, you don't get to play it that way, I'm not scared of you, and I'm not scared of the base because they're just as pissed off as me."

Scarborough was referring to Trump saying that the Mexican heritage of U.S. District Judge Gonzalo Curiel would prevent him from acting impartial in the case he's overseeing concerning Trump University.

Trump, the presumptive GOP presidential nominee, responded to Scarborough's tirade on Wednesday morning.

Nobody is watching @Morning_Joe anymore. Gone off the deep end - bad ratings. You won't believe what I am watching now! — Donald J. Trump (@realDonaldTrump) June 8, 2016

A day earlier, Speaker Paul Ryan and Senate Majority Leader Mitch McConnell blasted Trump for his remarks. Ryan called it the "textbook definition of a racist comment" and McConnell called Trump's comments outrageous.

CBS News' Katiana Krawchenko contributed to this report.