NY does not lean Dem, alot hinges on several factors. While Pataki isn't all that well liked, he does have alot of support and could still get reelected. If he runs for reelection it will be close between him and Spitzer. However, if Pataki abandons the Governor's mansion to run for President, or even for the Senate, and Guiliani takes over, Guiliani wins hands down against Spitzer.
Pataki's chances of getting re-elected are slim to nill. Polls show Spitzer winning by double digits. Spitzer's approval is in the 60's, Pataki's approval is in the 40's.