Romney Birther Joke Draws Obama Slam: 'America Doesn't Need A Birther-In-Chief'

President Barack Obama's re-election campaign intensified its rebukes of Mitt Romney Friday evening for a remark made by the presumptive Republican nominee about the president's birth certificate earlier in the day.

Speaking to a crowd of enthusiastic supporters in Commerce, Mich. -- and noting the local roots shared by him and his wife, Ann -- Romney quipped that "no one's ever asked to see my birth certificate. They know that this is the place that we were born and raised." Of course, Obama's birthplace has been the subject of fervid (if wholly debunked) conspiracy theorizing in the years since he arrived on the national stage.

The Obama campaign responded with a 15-second attack ad posted to YouTube Friday evening -- titled "America Doesn't Need A Birther-in-Chief" -- that recycles video of Romney's joke, while a narrator intones, "Holding out hope Romney had a vision for the middle class? Think again."

"Embracing unfounded conspiracy theories, distracting from real issues. America doesn't need a Birther-in-Chief," the voiceover continued.

The ad is the latest in a string of responses from the Obama camp to Romney's comment. First, a campaign spokesman slammed the Republican for "embrac[ing] the most strident voices in his party instead of standing up to them." Later, the president's official Twitter account followed with a barely veiled reference to the joke. The campaign also sent a fundraising email to supporters, with the subject line: "A new low for Mitt Romney."

Romney since insisted that he harbors no illusions about Obama's birthplace, telling a CBS News reporter that, "there's no question about where he was born. He was born in the U.S."

"This was fun about us, and coming home," Romney went on to say.