While it is a GOP-announced debate, the Democratic one probably will not be too far behind.  This is from www.politicalwire.com:

The South Carolina Republican Party is planning a presidential debate in May 2007 for GOP candidates running for the White House, according to CNN's Morning Grindnewsletter. Specific details for this forum are still being worked out.

Said the state GOP executive director: "Since 1980, no candidate has ever lost the (South Carolina) primary and gone on to be elected president. We believe it is a great test for Republican candidates."

Hotline On Call: "Recall that in 2003, ABC's George Stephanopoulos hosted the first-in-the-nation debate for Democrats in South Carolina."