Unless you believe that suddenly this country has a 44% evangelical population, you can probably drop the AP/GfK poll in the same circular file as Zogby's polls.
The conspiracy theories about polling are getting wackier by the moment. You've got whole swaths of conservatives that now seriously believe that the media is working in concert with the Democrats, Obama, ACORN, George Soros and about twenty other boogeymen (and I can tell you, Media Matters is getting kind of jealous at these Johnny Come-Latelies who are a part of the great left wing conspiracy) to fix the polls in favor of Obama.
Personally I don't believe the polls that show double-digit leads for Sen. Obama, simply because even with the failure of the Bush administration we still seem to be a closely divided nation. But neither do I believe the polls supposedly showing surges for McCain. I think we're at status quo in a 4-5 point race right now. Nor do I believe that McCain is looking at secret polls showing Pennsylvania tightening in his favor (yes, this is what conservatives are pushing around now - I read the con blogs and Free Republic so you don't have to). PA seems to me to be a lot like New Jersey for Republicans or Florida for Dems - constantly looks in sight, but at the last minute goes out of reach.
The right wants to have it both ways. They want the polls to be gospel truth when they showed Bush at 90% approval, when there was a slight majority in favor of war in Iraq, and when they show John McCain in the lead as they did after the convention. Otherwise, the low approval for Bush, the opposition to war in Iraq, and Barack Obama's lead in the polls are all inventions of the liberal plot.