In the AP poll that has been cited, 44% of its respondents identified themselves explicitly as evangelical Christians. So not too unusual that it would be so far towards McCain. Particularly when their likely voter model is also far more skewed towards 2004 numbers than what we see now from actual polls of the electorate. From registered voters, their numbers hit +5. From all adults, their numbers hit +10.
To put the problem of using the 2004 numbers for likely voters, Rasmussen's numbers, which are done from weekly tracking polls that survey 21,000 people over a period of six weeks, gives the Dems a 6.7 point advantage, which was NOT the case in 2004.