Top 10 reasons:
10. The DNC didn't target the undecided votes well. The RNC realized that almost all Republicans support Bush and almost all Democrats support Kerry and neither group will change easily. The RNC therefore effectively targeted the swing votes better.
9. The Republicans literally spent twice as much on the RNC as the democrats did on the DNC.
8. The RNC was a very well orchestrated event. Everything was timed to near perfection. All speeches were well scripted. However, the Bush twins' speech was obviously not written by them and their cuteness factor didn't quite cover up how fake that was.
7. In the DNC, they didn't nearly as aggressively attack their rivals.
6. Getting a disgruntled Democrat (Sen. Zell Miller) to give the keynote event and bash Kerry hard. He was so angry that when Dick Chaney came on right afterwards, he could bash as much as he wanted and sound calm and scholarly by comparison. That Democrat can be blamed for the bashing and still make the Republicans look good because he's not one of them technically.
5. The Republicans looked like they were having more fun. While the illusion that the Republicans were a hip party didn't quite work, the speeches for the most party were more entertaining.
4. The RNC was willing to lie and mislead far more boldly than the DNC, because they placed those statements so carefully in the convention.
3. Catchy imagery: Bush on the baseball mound, Bush standing on the Presidential Seal, Bush as a family man and all the love his family gives in very scripted moments, "W is for women" slogan, etc. Manipulative and obvious? Yes, but as a whole, almost as effective as Nixon's Checkers speech.
2. Saying that Kerry is a flip-flopper. This has been beaten to death and has been incredibly effective. Kerry has been a typical senator who goes with the best decision politically like all senators have to do. Dole did this 5 times more, but no one attacked him for it. There were times Kerry changed his mind, but they weren't typical of what he does.
And the number 1 reason...
1. Scaring the shit out of the public. Their message was "Vote for Bush. He'll go after those terrorists BEFORE they attack again. You're life is in danger with Kerry". This tactic won the election for Yeltsin in 1996. "Vote for me or you'll wind up dead with the other side"
This is not to say the DNC did not pull dirty tricks. The Republicans were just dirtier and more effective.
Extra: Just a few Misleading Examples. Please feel free to add your own.
1. Bush said that Kerry is fiscally irresponsible because he voted for a $2 trillion budget this year. He forgot to mention that his administration came up with the budget and he signed it.
2. Pataki said Bush created jobs. Sure Bush created jobs, but a lot less than the jobs he lost as president.
3. That Kerry would only go to war if the UN said it was OK? Kerry said he would got to war immediately and decisively if we were attacked. However he would only take us to war if he had to, not because it was popular.