Ambinder:

At least nine members of Congress have cosponsored a birther bill that would require prospective presidents to affirm their U.S. citizenship. What we don’t know is how widespread the belief is among Republicans — and even if the belief is confined to a narrow minority, whether the belief will spread as Republicans begin to pay closer attention to electoral politics in 2010 and 2012.  In the same way that Democrats in 2004 always got a stolen election question (which, to be fair, was at least closer to reality than the birther’s claims), Republican presidential candidates need to figure out how to diffuse angry birthers who are bound to show up and demand their attention.  …. The buried lede to this post: Rush Limbaugh claimed today that Obama "has yet to prove that he’s a citizen." Republicans have to be extra careful. If they give credence to the birthers, they’re (not only advancing ignorance but also) betraying the narrowness of their base. If they dismiss this growing movement, they might drive birthers to find more extreme candidates, which will fragment a Republican political coalition.

Uh, Marc? If they give credence to the birthers?

I’d say introducing, you know, actual legislation and stuff, counts as giving credence.