They're already taking shots at him. The DBM is playing wack-a-mole with him and Mitt, and it's Rudy's turn. So far the only one of the 'leading" candidates that they won't go after (at this time) is a certain senator from AZ.
As for the others (Duncan Hunter..etc) they have to show me that they can win, that they have the org, fund raising, pr flacks and the ability to (I'm not sure how to put this) speak to the American voter(?). Until they can do that I can't take them seriously.
That being said it's a long long time till NH, Iowa..etc and anytthing can happen...and probably will.
I'm not ready to drink anyones kool-aid at this time.