This election appeared to be gift-wrapped for the GOP a week out...
The two main factors in what went wrong are abortion and fraud and I don't know of a way to say which was the more major factor. Our voting system is basically FUBAR and needs to be replaced, and the abortion issue is something conservatives simply need to get over.
Joseph Farah's take on the fraud factor:
A rational approach to redoing our voting system would involve biometrics and p2p networking, and it just wouldn't be that difficult to eliminate fraud altogether at very little expense.