Dafydd does a thorough job with which I agree in great part. There are some issues regarding the Keating 5 McCain/Feingold legislation that affected the election that are important but they actually deserve a separate post.
The reductionist version:
1. If you promise less government and deliver more, you lose.
2. If you get caught stealing more than you can carry, you lose.
3. "Compassionate warfare" is worse than "compassionate conservatism" - See 1.
UPDATE: Michael Barone's take.