Giuliani is joke.
By now, the whole world knows that Rudy has had two or three really bad weeks, mostly having to do with abortion. He was never a pro-lifer, but he recently stated he favors public funding of abortion, and that does not support the Hyde Amendment (which bans public funding), but only would not actively work to repeal it. Well, that was obviously a nonstarter, so he has since backtracked. Exactly where we think he stands now, frankly I can't be bothered to find out.
Aside from abortion, Rudy is still a terrible candidate. Most of his supporters, like Andy McCarthy above, are myopic enthusiasts about one particular aspect of being President, and really never consider the totality of the job, and the campaigns required to get it. So to fully appreciate the wretchedness of the hypothetical Giuliani nomination, we have to have a little primer on Presidential candidates in general. Basically, you have to have all of three things:
1. He has to have the "right" policies or issue stances, both for the party he represents and for the country as a hole.
2. He has to demographically represent his party.
3. He has to have a good temperment for all aspects of the role.
The GOP is in a pickle right now because none of their declared candidates satisfy these basic, "have-to-have" criteria. But Guiliani is the worst of the lot, he independently flunks all three.
Besides abortion and gay rights, he's bad on immigration, he has no particular credibility on taxes, and he has no appeal to anyone with enthusiasm for limited government. This last point is flying under radar at the moment, but is very important nonetheless. A lot of Americans, not just tinfoil leftists complaining about HalliBushCo, are nervous about the unchecked growth of Leviathan in the era of the War on Terror, and Giuliani will not assuage their fears.
Demographically speaking Rudy doesn't represent New York (which would be bad enough), he's a real New Yorker. People who vote Republican in Presidential elections don't identify with New Yorkers.
Finally, Rudy is also a general jerk besides. It says a lot, that by 9/11, New Yorkers themselves had had quite enough of him, notwithstanding the fact that he is almost universally credited with saving the city. And working the Presidential campaign trail is like being in a boxing ring with Joe Louis, "You can run but you can't hide." He will be found out.