There's a difference between somebody who is poorly advised or "fooled", and somebody who deliberately lies. You can to some degree fix the former, by more thorough investigation, better advisers, or corrective education (as in the Miers case), but you can't fix liars.
Judging from Giuliani's track record, he has a pretty fair chance of being in the latter category.
Well, George W. Bush not only was “fooled” about Souter, he also lied about raising taxes. And I am sure you voted for him twice.
There is no evidence Giuliani has lied. You may disagree with him, but he never was a liar like Mr. Read My Lips was.