There's been no formal announcement of primary opposition, but Thomas Ravenel has hinted that he would run against Graham in the primary. There is also a "Draft Ravenel" website
http://www.petitiononline.com/ussc2008/petition.html So far the website hasn't received a lot of attention, but I, personally, think Ravenel has already made up his mind.
My gut tells me that Ravenel will be Graham in the primary and then go on to win the general election.