I hope Giuliani is NOT the nominee, but I disagree that he'd lose in a landslide, I actually think he'd win, and here's why:
The Italian-American vote. Yes, it matters. As someone of Italian descent myself, I realize how much that connection matters. Many members of my family both conservative Republican and liberal Democrat, have said they'd vote for Rudy in a heartbeat, primarily because "we need an Italian in there." I'm not the only Freeper to suggest this, and it has been mentioned before. I'd go as far as to say that it's the Italian vote that won him the NYC mayoral race. That may also have a lot to do with his endorsement of Mario Cuomo over Pataki. Not sure if that's necessarily a good thing, but it's a fact.
Italian-Americans make up a significant portion of NY and NJ and enough of PA, Ohio, and Michigan that all those states could easily be in his column. NY would actually be the MOST difficult to win, because they love Hillary up there and already lean Democrat.
He'd do less well in the South, but would still win, just not by Bush-like margins in states like GA and the Carolinas. Florida will be a toss-up as it was in '00 and '04 regardless of the candidate.
Disclaimer: I am NOT a Giuliani cheerleader. Just making a political analysis of such a race.