I've long supported the concept of separation of church and state. Many of my friends feel the same way. And, ultimately, many Americans feel the same way.
When you look at politics from the pulpit, you see that a majority (62%) of Americans don't want to be told who to vote for, or to have political speeches given from their religious leaders, which makes sense to me. Of course, I don't like the idea of anyone telling me who to vote for, so it would make sense to me to keep church separate from politics here to me.
Interestingly, in the article linked above, it shows that 29% of pollsters said they were less likely to vote for Giuliani now that Pat Robertson has endorsed him, as opposed to 6% who said they were more likely to. There were only 1000 people polled, so it may not have the highest rate of veracity. But still, that is something that Giuliani's camp might want to think about.