Trump, After Becoming Presumptive Nominee: 'We're Going After Hillary'

We 'Don't See You as a Friend': Laid-Off Coal Miner Confronts Hillary in WV

WATCH: Trump Connects Cruz's Father to Lee Harvey Oswald

After his dominant win in the Indiana primary, Donald Trump is turning his attention to Hillary Clinton and the general election.

On "Fox and Friends" this morning, the presumptive Republican presidential nominee said that he's going to be building a larger general election staff and a fundraising apparatus.

Trump said that he's confident in his ability to defeat Clinton, calling on skeptical Republican lawmakers and voters to unite behind his campaign.

He added that he's been surprised that some of his former adversaries have reversed course and asked to join his team.

"I'm getting calls from people that have said such terrible things about me, and now they want to join," Trump said.

He noted that just yesterday, he received a call from someone who had said "unbelievably horrible" things about him in the media, who apparently has changed his mind and now wants to support Trump.

"I actually asked him, 'How do you do that? How do you pivot?'" Trump said. "They're all wanting to join, and we'll see what happens."

Trump declined to reveal who that person is, but he said he's glad to see people coming to his side.

Watch more above.

RNC Chair: 'Trump Will Be the Presumptive Nominee'

‘A Brave New Orwellian World’: Judge Nap Slams Ruling on Locked iPhone

Man Shot Dead Trying to Break Up Domestic Dispute Outside Walgreens

'Check Your Privilege': MO Campus Posters Call Out 'Christian Privilege'