The latest Pew poll, showing a three-point lead for Obama (down from five points in June), has McCain increasing his margin among Protestants from one point to seven–entirely from evangelicals, since he’s lost three points off his margin among mainliners. Obama, meanwhile, has gained ground among Catholics, increasing his margin from two points to five. That’s thanks to a shift among white Catholics who in June were supporting McCain by six points and now just by one. Nationwide, white evangelicals support McCain 68-24 (hello, Barna?) and white mainliners 50-39. In 2004, John Kerry lost the Protestant vote to George Bush by 19 points and the Catholic vote by five. So Obama is currently running ahead of Kerry in both cases by the nearly identical margins of 12 and 10 points respectively. White mainline Protestants are moving away from McCain and white Catholics are headed in Obama’s direction. I’d say it’s time to start writing stories about McCain’s Catholic problem.