Can you expand on this? Logic would dictate that Giuliani being the current leader has the most votes to lose.
Sure. Rudy may have the MOST to lose but that does not mean he is most LIKELY to lose it.
Thompson is now the great conservative alternative hope so he will appeal to those who feel Rudy is not conservative enough. These anti-Rudy votes NOW go to Romney, the lesser candidates, or Newt NOT Rudy. So he doesn't lose there. McCain will bleed votes who have gone to him in desperation to defeat Rudy and McCain might even give it up and endorse Fred (which in my mind would be the only way he could become a major threat to Rudy.)
Most of Rudy's support believes him to be the best candidate available in spite of some of his past policies. So it is fairly firm.