Poll: 31% of Republicans and tea partyers doubt Obama's citizenship

The Washington Post/ABC News poll includes another bite at the birther apple, asking whether Americans have "suspicions" or "solid evidence." Among all Americans, 68 percent say Obama was definitely born in the United states, while 14 percent speculate about another country and the rest don't know; asked whether it was "your best guess that Obama was born in the United States," the "yes" number rises to 77 percent.

So who are the "birthers"? Mostly Republicans and "very" conservative voters.

Thirty-one percent of Republicans doubt Obama's citizenship; the doubters also include 31 percent of tea party movement supporters, 36 percent of very conservative voters, and 27 percent of somewhat conservatives. Every other subgroup is under 20 percent.

But at this point we could have predicted that -- birtherism has remained a stubborn belief in the conservative base, despite widespread denunciation from elite conservatives. The more interesting part of the poll is that 31 percent of people who think Obama was born in another country approve of his job performance, and 34 percent give him a favorable rating. That validates a theory of mine -- that many so-called birthers don't actually hold Obama's (to them) foreign-ness against him, or think it's a way to oust him from the presidency. They have little information, they know he's half African, and they jump to conclusions.