Bennett was caught on tape telling a Republican Party meeting his theory shortly after announcing his support for presumptive Republican presidential nominee Mitt Romney:
"I know there's a lot of people who are skeptical as to whether the president was born in Hawaii," he said. "Personally, I believe he was. I actually think he was fibbing about being born in Kenya when he was trying to get into college."
He went on to accuse Obama of spending millions on attorneys to have his college records sealed.
"So if you're spending money to seal something, that's probably where the hanky panky was going on," he went on.
KPHO-TV, Phoenix, said the video was posted on YouTube Monday.
Arizona House Minority Leader Chad Campbell accused Bennett of being unethical for making such remarks.
"I think maybe [he is] trying to cater to this extreme fringe of voters," Campbell said. "Does he want to be a political operative or does he want to be secretary of state?"
Later, Bennett told The Arizona Republic his comment hinged on the word "if." Bennett said he never meant to make an unconditional statement.
"I have no personal knowledge about what happened," Bennett said in backpedaling, adding he has no plans ever to mention so-called "birther" theories again.
The Republic noted there is no record Obama ever claimed he had been born in Kenya. A partner in a literary agency admitted to Yahoo! News last month the issue was the result of a fact-checking error in a Harvard brochure that inaccurately described Obama as having been born in Kenya and raised in Hawaii and Indonesia.