Mr. Harrell will serve as co-chairman of Mr. McCain's presidential exploratory committee in South Carolina and as national co-chairman of Legislators for McCain.
Other influential South Carolina politicians - including Attorney General Henry McMaster and Senate President Pro Tem Glenn McConnell - have shown support for Mr. McCain, R-Ariz., having joined his Straight Talk America political action committee.
"But with Bobby on this team, it's probably the biggest shot of momentum we've had since we began," said U.S. Sen. Lindsey Graham, R-S.C. "What people see in Bobby at the Statehouse, people throughout the country will soon see - a man dedicated to moving our state and our nation forward."
Blease Graham, who teaches at the University of South Carolina, said Mr. McCain is sitting pretty in South Carolina.
That doesn't mean there's no hope for other Republicans fighting for the party's nomination in 2008, he said.
Among the questions: How Mr. McCain's support of more troops in Iraq will play across the country and in South Carolina, where the military influence is strong.
Mr. McCain and Lindsey Graham criticized congressional colleagues who were considering a resolution denouncing the buildup.
"Rather than a resolution of disapproval, which I don't think is an act of political courage, go ahead and vote to cut off the funds," Mr. McCain said.
A year before South Carolina's presidential primaries, it's difficult to know how Mr. McCain's Iraq position will be perceived, Blease Graham said.
If more troops are sent and the situation in Iraq doesn't improve, President Bush will get the blame, but the issue will be a challenge for Mr. McCain, he said.
Reach Kirsten Singleton at (803) 414-6611 or firstname.lastname@example.org.
Mr. McCain is the fourth potential presidential candidate to visit South Carolina in the past week.
New Mexico Gov. Bill Richardson, who has yet to announce whether he'll seek the Democratic nomination, spoke Friday and Saturday in Columbia and Greenville.
U.S. Sens. Joe Biden, D-Del., and Chris Dodd, D-Conn., attended Martin Luther King Jr. Day celebrations Sunday and Monday.
- Morris News Service