Ed Driscoll has a very nice piece entitled "Obama Gets Left Behind" The Preference Cascade Begins to Build.
I'd add a couple points to the argument.
1. The Obama Administration severely miscalculated on the contraception issue. They tried to force something on the Catholic Church and they were completely caught unaware by the resistance they met. Now the Administration is being sued by the Catholic Bishops and the religious Right to Life are asking why they are supporting this guy? Sure the bible says "give unto Caesar" but the idea that Obama thinks of himself as Caesar is in itself off-putting.
2. The "Polish Death Camps" gaffe was an unforced error but the unwillingness to apologize was hubris. Combined with the Catholic contraception issue - the support of many Polish-Americans who may normally vote Democrat now may be in play. This demographic may be the deciding factor in many battle-ground states.
3. One parallel to the preference cascade that bears mentioning is how people self-report. Many Democrats may be saying they are supporting Obama when asked by pollsters but may act completely different when alone in the voting booth. Don't be surprised if the polls are found to be off by a big factor the day after the election.