"I heard he was a terrible student, terrible. How does a bad student go to Columbia and then to Harvard?" Trump said in an interview with The Associated Press. "I'm thinking about it, I'm certainly looking into it. Let him show his records."
Obama graduated from Columbia University in New York in 1983 with a degree in political science after transferring from Occidental College in California. He went on to Harvard Law School, where he graduated magna cum laude 1991 and was the first black president of the Harvard Law Review.
Obama's 2008 campaign did not release his college transcripts, and in his best-selling memoir, "Dreams From My Father," Obama indicated he hadn't always been an academic star. Trump told the AP that Obama's refusal to release his college grades were part of a pattern of concealing information about himself.
"I have friends who have smart sons with great marks, great boards, great everything and they can't get into Harvard," Trump said. "We don't know a thing about this guy. There are a lot of questions that are unanswered about our president."
Katie Hogan, a spokeswoman for Obama's re-election campaign, declined to comment.
Trump, a wealthy businessman and reality TV host, has risen to the top of many polls in part by his outspoken call for Obama to release his long form birth certificate. The state of Hawaii has released a certificate of live birth indicating Obama was born there on August 4, 1961, but that has not quelled critics who believe Obama was born outside the United States and is therefore not qualified to be president.
The so-called "birther" controversy has dominated the early stage of the 2012 GOP nominating contest, with Trump leading the charge.
"I have more people that are excited about the fact that I reinvigorated this whole issue," Trump said, adding "the last guy (Obama) wants to run against is Donald Trump."
Trump is scheduled to travel to the early primary states of New Hampshire and Nevada this week and said he will make a final decision about a presidential bid by June.
Also in the AP interview, Trump:
- Said Republicans had made a mistake by embracing a budget proposal crafted by Wisconsin GOP Rep. Paul Ryan that included deep cuts in Medicare. "The seniors are afraid. The plan Paul Ryan put forth has made the Democrats so happy," Trump said.
- Declined to disclose his net worth, saying he'll do so if he decides to run. "You'll see what it is, possibly, very likely, in the next 4 weeks. I don't want to say because I don't want to ruin the press conference," he said.
- Expressed surprise that the 2008 GOP nominee, John McCain, had suggested Trump's effort was a publicity stunt. "I congratulate him for getting the attention he's getting," McCain told NBC's "Meet the Press" Sunday.
Trump said he had been a big supporter of McCain. "I would find it hard to believe he would say anything bad because I raised a fantastic amount of money for him," Trump said.