Hollywood actor Fred Thompson plans to run for US president in 2008.
Mr Thompson, a 64-year-old social conservative, said he was planning a campaign that will use blogs, video posts and other internet innovations to reach voters turned off by "politics-as-usual" in both parties.
He had previously won election twice as a Republican senator from Tennessee.
A political adviser said Mr Thompson had tentatively decided to run for president and that he has quit his role on the TV crime series Law & Order. He will now begin raising money to gauge support.
Mr Thompson told USA Today: "I can't remember exactly the point I said: 'I'm going to do this. But when I did, the thing that occurred to me: 'I'm going to tell people that I am thinking about it and see what kind of reaction I get to it.'"
Mr Thompson joins a crowded Republican field with no dominant choice. The current front-runners include former New York mayor Rudolph Giuliani, Senator John McCain of Arizona and former Massachusetts governor Mitt Romney.
President Bush, prohibited from running for a third term in November 2008, is set to leave office in January 2009.