A lot of states incl big delegate states like CA, favoring Giuliani will hold their primaries on the Supertuesday - Feb. 5, as well as a lot of Southern States, benefitting Thompson.
The thing is though, CA and NY have more delegates between them than all of the Southern states voting on Feb. 5th combined. I think the list of Feb. 5th states clearly favors Giuliani. If he wins CA, NY, NJ, and just a couple of others (say CO or IL), then I think he builds a clear delegate lead, even if Thompson sweeps the South. But Giuliani's problem is that he has to at least do well enough in the states that vote in January that his leads in places like CA doesn't collapse.