Donald Trump isn't even running for president yet, but he is already gearing up for the primaries by pandering to the Republican base.

In an interview with ABC News' Ashleigh Banfield that aired Thursday, Trump said he had some doubts that President Barack Obama was a U.S. citizen.

"Everybody that even gives any hint of being a birther -- a word you didn't use -- even a little bit of a hint like 'gee, you know, maybe, just maybe this much of chance,' they label them as an idiot," he told Banfield.

"Let me tell you, I'm a really smart guy," Trump continued. "I was a really good student at the best school in the country. The reason I have a little doubt -- just a little -- is because he grew up and nobody knew him."

"When you interview people, if I ever got the nomination, if I ever decide to run, you may go back and interview people from my kindergarten. They'll remember me. Nobody ever comes forward. Nobody knows who he is until later in his life."

"It's very strange. The whole thing is very strange," he added.

If the American business magnate wants the Republican nomination then he may need support from the birthers. A recent PPP poll found that a majority of Republican voters don't believe Obama was born in the U.S.

Trump also took issue with Republican House Speaker John Boehner's emotional outbursts.

"I don't like the crying," he said. "I do not like it. I don't understand it. I really like him as a person. I think the crying is an emotional thing that frankly, probably makes him a very nice man. But you know, I don't like to see it in a leader."

Trump told Banfield that he was prepared to spend $600 million of his own money if he does decide to make a run for the White House.

"That's one of the nice things. I mean, part of the beauty of me is that I'm very rich. So if I need $600 million, I can put $600 million myself," he said.

This video is from ABC's Good Morning America, broadcast March 17, 2011.