Republicans can't stand their own candidates
Why else would Fred Thompson, who hasn't even announced yet and hasn't participated in any debates, be the leading Republican candidate in South Carolina? His website has links to help you give him money, raise money for him, ask friends to give him money, call talk radio, etc., but his political positions are buried within his biography - basically nobody has any real idea of what he would do as President. They just know that he isn't Mormon (Romney), doesn't support "abortion on demand" (Giuliani), and isn't a "maverick" (McCain). As long as Fred Thompson doesn't open his mouth and try to say anything substantive, he doesn't alienate anyone. Looks like right now, that's good enough.