House Speaker Paul Ryan Dismisses Idea of Convention Challenge to Donald Trump

“The way I see it is he won the thing fair and square,” Ryan said.

"Seventeen people competed, one person won and he got the delegates," Ryan added. "The delegates ultimately decide these things, but he won fair and square."

But some Republicans, including Weekly Standard editor and ABC News contributor Bill Kristol, have not lost hope of recruiting a third party alternative to the billionaire businessman, or of using the rules of the convention to block Trump's nomination.

The house speaker endorsed Trump last week in an op-ed for The Janesville Gazette.

"I feel confident he would help us turn the ideas in this agenda into laws to help improve people’s lives. That's why I'll be voting for him this fall," Ryan wrote.

See more of Speaker Paul Ryan’s interview Sunday morning on “This Week.”