The reason Rudy is ahead in the polls right now is because people see him as a tough leader. Once his liberalism comes to the front and center though, he's toast.
If Dunkan remains strong and sticks to his guns, he could easily take Rudys place at the front of the line.
People want a strong leader. They don't want another 8 years of "mush."
I like Bush personally, as a man, but as a president he wasn't strong enough to stand up to political correctness (the censoring of any objection to the liberal agenda).
Also Rudy has more general population name-recognition, whereas the nation hasn't heard as much about Duncan Hunter. Yet.