Bush Could Appoint Himself!!!
This is an interesting situation:
Say something similar to what happened in 2000 happens again in 2004. We have a contested election, and there is a debate over whether or not to count some number of votes - a debate that could well decide who became president, like in 2000.
The debate goes to the Supreme Court.
Rehnquist has cancer, and it's currently unclear whether or not he is going to be able to serve his term. What happens if he is unable to serve and is effectively forced to leave before the end of the year?
Bush appoints a Supreme Court justice to serve in recess between now and when the Senate reconvenes in 2005 (I believe). The senate would not have to confirm that justice.
Given the way the court is divided, Bush's appointee would probably make the difference in any decision over a contested election.