Obama ad slams Romney as "birther-in-chief"

(CBS News) Seizing on an uncharacteristic joke Mitt Romney made Friday about the president's birth certificate, the Obama campaign is out with a new web ad arguing, "America doesn't need a Birther-in-Chief."

"Holding out hope Romney had a vision for the middle class? Think again," a voice in the ad says, introducing a clip of the presumptive Republican nominee at a rally Friday in his home state of Michigan. While celebrating his roots, Romney abandoned his typically dogged refusal to engage "unfounded conspiracy theories," as the ad calls them, that the president wasn't born in the United States.

"I love being home in the place where Ann and I were born and raised, where both of us were born," Romney said Friday. "Ann was born in Henry Ford Hospital; I was born in Harper Hospital. No one's ever asked to see my birth certificate. They know that this is the place that we were born and raised."

(Watch: Romney: "No one's ever asked to see my birth certificate.")

Following the rally, Romney said in an interview with CBS News' Scott Pelley that the remark was merely "a little humor," and wasn't meant as a tossed bone to the far right wing of the party. Despite his alliance with Donald Trump - perhaps the most outspoken "birther" of all - Romney has maintained his disagreement with the real estate tycoon on the issue.

"I've said throughout the campaign and before that there's no question about where [Obama] was born; he was born in the U.S.," Romney told Pelley. "I've said that probably 30 times by now, and 31 certainly won't hurt."

But the Obama campaign is cashing in. Along with the web ad, a fundraising email titled "A new low for Mitt Romney" went out to supporters almost instantly following the rally, asking supporters to "take a moment or two to think about [Romney's remark], what he's actually saying, and what it says about Mitt Romney."