Former U.S. Sen. Fred Thompson on Thursday said Newt Gingrich will not be an "uncertain trumpet" if he's elected president of the United States.

Thompson, a former actor and 2008 GOP presidential candidate, campaigned for Gingrich at the Georgia Capitol. Surrounded by about a dozen state Republican lawmakers, Thompson said Gingrich will provide leadership that "is bold, unafraid, not timid" and said the former Georgia congressman "understands the frustrations and concerns of the American people."

Thompson represented Tennessee in the U.S. Senate from 1994 until 2003. As an actor he is perhaps best known for roles in "The Hunt for Red October," "Die Hard 2″ and the television series "Law & Order." He endorsed Gingrich for president this week.

In response, state Rep. Lynne Riley, R-Johns Creek, who is supporting former Massachusetts Gov. Mitt Romney for president, said Gingrich "has spent the last decade running from his Georgia roots and into the arms of the Washington insider establishment."

Riley said Romney "will never embarrass the people of Georgia."