Former presidential candidate Ben Carson said if it came down to it, he would advise GOP front-runner Donald Trump not to run as a third party candidate.

Fox News host Greta Van Susteren asked the Trump endorser late Friday if he would instruct the New York billionaire if he would rescind his Republican pledge to support the eventual nominee and pursue an independent run after the July convention.

"No, because that would absolutely guarantee a win for the Democrats and what all the conservatives must remember is that that will guarantee two to four Supreme Court picks that will be progressive, even though that's not the word that really describes him and that will severely alter the future of this country," Carson said.

Trump, who leads the party with the most delegates, has recently lost primaries to runner-up Sen. Ted Cruz, as "Never Trump" advocates rally around the Tea Party Texan and third-ranked Ohio Gov. John Kasich.

But Carson warned the GOP establishment and members of Congress from changing convention rules in order to block Trump from winning the nomination.

"One of the things that the Rules Committee is going to have to decide is, is it worth losing everything in order to manipulate the will of the people or do you want to have rules that honor the will of the people?" Carson said. "Because, if you do that, you will gain a lot more enthusiasm and the millions of people who have brought in will actually grow to even more and they will be enthusiastic and they will defeat the Democrats. But if you dampen that enthusiasm, it doesn't matter what you do, you're going to lose."