President Obama is laughing off lingering doubts about his birth certificate. The commander-in-chief cracked wise at a fund-raiser in Boston, poking fun at the so-called "birther" movement, which insists he is not a natural-born citizen. "There's no weakness in us trying to reach out and seeing if we can find common ground," he said Tuesday. "Now, there are going to be times where we can't. I was born in Hawaii. What can I say? I mean, I just ... I can't change those facts."