For months, Mitt Romney has used his considerable weight in the GOP in a public effort to stop business mogul Donald Trump from capturing the nomination. He recorded robocalls for Florida Sen. Marco Rubio before he dropped out, campaigned with Ohio governor John Kasich, and eventually voted for Texas Sen. Ted Cruz in the Utah caucuses

Now, Romney is lamenting the splintering of the opposition to Trump. In a podcast recorded with CNN's David Gregory, Romney said that Trump would likely clinch the delegates needed for the nomination before the convention in Cleveland if neither Cruz nor Kasich drop out.

When asked whether he thought there would be a contested convention, Romney said, "You know, I think that depends on whether or not Mr. Cruz and Mr. Kasich both stay in the race aggressively through California. If they're both going at it aggressively, right until the very end, then I think it's very likely Mr. Trump wins on the first ballot."

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He went on.

"I say that because I think that Mr. Cruz and Mr. Kasich divide the vote, if you will, and that would make it easier for Mr. Trump to win the winner-take-all congressional districts and the winner-take-all states and get the delegates he needs either hit the 1,237 or to get close enough to it that he could sway the uncommitted delegates that he'd need to get the victory on the first ballot."

"If it remains three candidates," Romney said, "I think Mr. Trump gets it on the first ballot."

In March, Romney gave a speech blasting the Republican front-runner, calling him a fraud, and encouraged Republicans to partake in "strategic voting" and vote for whatever non-Trump candidate has the best chance in any particular primary. Cruz won the Utah caucuses. And Kasich won Ohio, giving him the rationale to stay in the race.

In the preview clip posted by Gregory's team, Romney did not comment on whether he was partially responsible for a splintered opposition, given that he chose to help out multiple candidates instead of just endorsing one from the start.

But Romney did reaffirm his strong belief that Trump is a danger to Republicans and said that he felt that he had to speak out.

"At some point, you do what you think is absolutely right," Romney said. "And I simply could not stand by and say nothing about a candidate who I thought was taking the party and potentially the country in a very unfortunate direction.

'So I said what I believed, that may not make me real popular in a lot of corners. But frankly, the worst thing that could possibly happen to me politically has already happened. So I'm not going to worry about that very much."

Romney also said he has no sympathy for Trump's struggle to secure friendly delegates for the convention.

"Campaigns have to be able to navigate those rules," Romney said. "And by the way, there's probably nothing wrong making it difficult. After all, these rules are a lot simpler than the rules of foreign affairs for instance or the rules of our economy. And if you want to be president, you're going to have to deal with things far more complicated than Republican delegate rules."

Romney told Gregory that delegates might be in for some unique wining if there's a contested convention, something Trump himself has alluded to.

"That's the nature of the process," Romney said. "My guess is some delegates might like to fly around on Air Trump or perhaps get a membership to Mar-A-Lago.

"I think there's a lot of ways to be persuasive on the part of the people who are close and there will be quite a few uncommitted delegates that go to Cleveland. And being able to pick off 50 or 100 of them is probably not beyond the possibility of a strong campaign. "

Romney's criticism is a stark change from the 2012 campaign, when the former Massachusetts governor actively sought Trump's support, appearing alongside him in Nevada and saying that he was "honored" by his endorsement.

"Donald Trump has shown an extraordinary ability to understand how our economy works," Romney said at the time.