Donald Trump's new convention manager, Paul Manafort, said Friday that he's confident the GOP front-runner will have clinched the 1,237 delegates needed to win the GOP nomination at least a month before the July convention.

"The reality is Ted Cruz has seen his best day. The reality is this convention process will be over with sometime in June, probably June 7," Manafort said on CNN's "New Day" Friday morning. "And it will be apparent to the world that Trump is over the 1,237 number. And at that point in time when it is apparent, everything will come together."

Manafort was recently hired to work alongside campaign manager Corey Lewandowski to ensure the business mogul comes out of the convention as the nominee, even if he doesn't reach the necessary number of pledged delegates ahead of time. Sen. Ted Cruz's recent successes on the campaign trail, especially his landslide win in Wisconsin, have prompted many to say Trump is no longer inevitable.

"Because the campaign comes in stages, he understands there's a time where winning isn't enough. It's how you win and how much you win," Manafort said when asked why he was hired to join the campaign.

Trump's next big contest will occur on April 19 in New York, when he is expected to win the winner-take-all primary.