Easy. He is the 'front-runner' in a plurality sense because of name recognition. He gets the third that will always go with the yard sign they last saw. He has little else to recommend him. But thanks for asking.
I am not a Rudy supporter, but I am open to his candidacy. But if you honestly believe the people here on FR who are supporting Rudy are the type that "go with the yard sign they last saw," I've got to wonder about that.