It wouldn't take too much to cause certain types of conservatives to stay home, especially if they convince themselves any differences between the parties (or their candidates) are so small as to not make it worth the effort to vote.
This may be why the Republicans are trotting out things such as the marriage amendment and the flag protection amendment. Some people need that sort of reassurance.
Those are the people who are truly freaking BRAIN DEAD!
When you take a hard look at who the RATS would install as committee chairman, AND UNDERSTAND THE RAMIFICATIONS, you understand the differences are huge. Imagine only Ruth Bader Ginsburg type nominees for SCOTUS getting a vote. All those WHINERS who complain about Bush, imagine a Kerry or Gore presidency. If you think the differences are too small, you need to be committed to an insane asylum.