In 2014, Trump said that black people were falsely claiming

they'd been born in Kenya to help them get admitted to college and to get better financial aid -- and so maybe Obama had done that.

So it wasn't just Obama, according to Trump. He said "people were doing that." It was a thing black people did.

http://abcnews.go.com/Politics/donald-trump-perpetuated-birther-movement-years/story?id=42138176

Speaking at the National Press Club, Trump says he doesn’t regret questioning President Obama’s citizenship, and there’s a “chance” he was born in the United States. He also speculates that President Obama wrote he was born in Kenya on his college applications to receive more financial aid.

"So look there are three things that could happen. And one of them did happen. He was perhaps born in Kenya. Very simple, okay. He was perhaps born in this country but said that he was born in Kenya. Because if you said you were born in Kenya, you got aid and you got into colleges. And people were doing that," Trump said. "So perhaps he was born in this country, that has a very big chance. Or you know, who knows."