This, from PPP, is disturbing:

Only 38% of Republican primary voters say they’re willing to support a candidate for President next year who firmly rejects the birther theory and those folks want Mitt Romney to be their nominee for President next year. With the other 62% of Republicans- 23% of whom say they are only willing to vote for a birther and 39% of whom are not sure- Donald Trump is cleaning up. And as a result Trump’s ridden the controversy about Barack Obama‘s place of birth to the highest level of support we’ve found for anyone in our national GOP polling so far in 2011.

That Trump is leading in the national polls is almost meaningless in terms of who gets the nomination, less so in terms of telling us something about the character of the Republican base. What’s news is the idea that the birther theory is so entrenched that so many Republicans won’t support a candidate who completely rejects it.

As Brendan Nyhan points out, the summary is a bit misleading however, as a good 39 percent say they “aren’t sure” if they’d be willing to support a candidate who rejected birtherism, and the 38 percent who would are far larger than the 23 percent for whom it’s an absolute dealbreaker. The elite anti-birther backlash may also shift those numbers.