Let's ignore those who vote exclusively along party lines. That leaves only independents, moderates, and single-issue votes.
Now.
Rudy's stance on the 2nd Amendment will cost him support from the NRA and Pro-Gun Rights Democrats (and yes, they do exist).
Rudy's stance on abortion and homosexual marriage might cost him the vote of a portion of the Reagan Democrats, particularly concerning the former part than the latter (how many votes his stance on abortion costs him will depend on how many decide to go third party/not vote at all).
Rudy's stance on illegal immigration (and I'm talking about his record, not the pandering he's doing right now) will most likely cost him the votes of the border states who are most heavily affected by illegal immigration. Think they'll choose another Pro-Amnesty candidate after Bush?
And his marital/personal issues - which seem much more problematic than those of other candidates - might cost him the votes of people who care about. I personally don't make it my sole deciding factor, but there are people who will (ironically, this is an area where Hunter has far less problems; married once, and has remained with his wife for years, and has two sons; one of whom is an Iraq War Veteran running for his father's old spot in office, and the second son comes here to FR on behalf of his father's campaign).
His fiscal conservatism. Although this is his strong point, looking at his record in the final years of his mayoral term reveals lots of spending and other troubling issues, so this might cost him some of the big business/Country Club Republicans.
Judges. A deciding issue for many people who realize how big an issue judges are, and Giuliani's record isn't good here. Some might retort that he was constricted by the Judicial Committee that selects what judges a mayor can appoint...but this becomes mute once you realize that the members of this Committee are selected by the Mayor. So the overwhelming amount of liberal judges he appointed does not speak well of him.
A lot speak of how much the media tried to criticize him in New York, and how that's a positive. Let's think about that: he brought down crime (which all liberals hate, for some reason). He brought down taxes (same thing). He supports Bush. He supports the War on Terror. And, most of all, he's a REPUBLICAN. Can't let Republicans look good, no matter how much they are alike to the liberals ideologically.
And also, if it comes down to Rudy vs. Hillary...who do you think the media will side with? Be honest. And remember that nearly 50,000,000 people voted for Kerry.
So he's spoken out in support of the War on Terror (not a unique trait amongst the candidates). He's a fighter against the media (again, not a unique trait; he just gets more screentime). A lot of people think of him in connection with his performance with 9/11, which is fine...but it's not an ideal way of picking a Presidential candidate.
Looking at all of this, I can only conclude that nominating Rudy will alienate Reagan Democrats and conservatives. Party-line voters will vote Republican/Democrat no matter who the nominee is, so the independents and moderates will decide everything. And these above issues will alienate a good many of them.
But hey, Hillary's not doing so well in head-to-head votes with candidates. Many people are going into the election with a mindest of "ANYONE BUT HILLARY."
So taking all of this into mind...noting that Giuliani will alienate a portion of the voting base, and noting that many people are against Hillary...doesn't it make sense to support a more conservative candidate? ESPECIALLY when we're not even at the primaries yet?
Think about it.