He's batshit crazy.
No, wait, that's why he's running in the first place.
No, he supports people like this:
“He’s one of the people I admire most in the world, and if most people did half the good that Alan’s done, the world would be a wonderful place.”
[Alan] Placa (by his own admission) is referred to as “Priest F,” a Priest who engaged in pedophilia.
I am going to go out on a limb here and say that the voting public is generally negative about child molestation. So, Giuliani supporting a priest who's tied up in the whole Chruch abuse scandal is – I'm guessing – a bad thing.
More importantly, the skeletons and blunders just seem to be sprouting out of the woodwork for Giuliani – the above linked article mentions the Kerik fiasco and Rudy's attempts to assume extralegal authority following 9/11, for example, and that's not even the half of it. And it's not even the general campaign yet. The press has yet to focus, laser-like, on discovering any and everything wrong with him and bringing it to light (If, you know, they ever will. He's got that patented conservative steely-eyed gaze that turns all the reporters into squeeling girls. That manly musk that turns all the pundits into panty tossing concert goers. That x-factor that turns his failings into a giant blind spot.) so who knows just what we're going to find out in a few months time? What we're seeing, with all these scandals, is a narrative being constructed that there's something not quite trustworthy about Giuliani. It's not too late for him to turn it to his advantage, of course, with that gigantic “me against the world” chip on his shoulder feeding into the conservatives feelings of being an oppressed minority (Or, you know, rich, white Christians.). But, eventually, even if one of these scandals doesn't stick, the narrative will.