First elected in 2004, Chapman has often acted independent of the Republican leadership, especially with regard to the issue of eminent domain and the future of Jekyll Island.
"When I look for a person I'm voting for, there are certain things I look for, and I try to be that," he said. "You shouldn't focus so much on who's for it and who's against it but just do what's right for the people."
Chapman's decision brings to seven the number of GOP candidates, including Insurance Commissioner John Oxendine, Secretary of State Karen Handel, Congressman Nathan Deal, state Sen. Eric Johnson, state Rep. Austin Scott and businessman Ray McBerry. Four Democrats have announced: former Gov. Roy Barnes, Attorney General Thurbert Baker, former Adjutant General David Poythress and House Democratic Leader DuBose Porter.
Chapman's first challenge will be getting known, said Merle Black, a political science professor at Emory University.
"It's a big Republican field, and many of them are quite unknown," Black said. "Why does he think he can win?"
Chapman wasn't discouraged Thursday. He said with modern technology, developing name identification can be done quickly.
"I believe when people sense you're committed to doing things for the common good, that message will spread fast," he said.
Chapman's opposition to the state's deal with Linger Longer Communities to redevelop Jekyll Island has given him name recognition among conservationists around the state.