“We have a problem in this country. It’s called Muslims.
“We know our current President is one. You know he’s not even an American," the audience member said to Trump.
Trump has since defended his decision not to correct the man.
“The media wants to make this issue about Obama. The bigger issue is that Obama is waging a war against Christians in this country. Christians need support in this country. Their religious liberty is at stake," Trump said in a statement.
Democratic National Committee Chairwoman Debbie Wasserman Schultz called Trump a racist.
"GOP front-runner Donald Trump's racism knows no bounds. This is certainly horrendous, but unfortunately unsurprising given what we have seen already. The vile rhetoric coming from the GOP candidates is appalling.
"(Republicans) should be ashamed, and all Republican presidential candidates must denounce Trump's comments immediately or will be tacitly agreeing with him," Schultz said.