Enter Thompson (finally) stage right

After months of flirting, Fred Thompson finally announced his candidacy for the 2008 Republican presidential nomination – on a late night comedy show.

"I am running for president of the United States," the veteran lobbyist, politician and actor from Tennessee said on NBC's The Tonight Show with Jay Leno. His announcement was taped in advance.

True to his Hollywood roots, he picked the same venue that launched the political career of Arnold Schwarzenegger, another high profile actor-turned-politician. Mr Thompson's laid back, good-ole-boy style masks an ambition and drive that has already propelled him to the front of the Republican field. For all the late-night banter, he steadfastly supports George Bush on Iraq. And like the Mr Bush, he does not want to withdraw forces from what he calls a central front in the "war on terror".

"Our courage as a people must match that of the brave men and women in uniform fighting for us," he said. "They know if we abandon our efforts, or appear weak and divided, we'll pay a heavy price for it in the future."

Late night comedy programmes – such as Mr Leno's and Bill Maher's on HBO are being courted by candidates from all parties – far more so than serious-minded news programmes.

The former star prosecutor from the TV series Law & Order followed up his announcement with a webcast outlining his reasons for running, which included threats to US national security and the economy. Despite a political and lobbying career as the consummate insider, Mr Thompson fell back on the perennial call for change in Washington, which always appeals to the Republican heartland voter.

"I do not accept it as a fact of life beyond our power to change that the federal government must go on expanding more, taxing more and spending forever," he said.

Mr Thompson, 65, is trying to reach the conservative base, which has yet to pick a favourite from a lacklustre slate of candidates. Some political observers say he is already too late in entering the race months after his rivals, who have been crisscrossing Iowa, New Hampshire, South Carolina and beyond, even though the first primary voting is still four months away.

But for many conservative voters, the arrival on the scene of a candidate in the mould of Ronald Reagan is a relief. Mr Thompson last night dismissed suggestions that he took too long to join the race.

"I don't think people are going to say, 'You know, that guy would make a very good president, but he just didn't get in soon enough,"' he told Jay Leno. "If you can't get your message out in a few months, you're probably not ever going to get it out."

Mr Thompson's polling numbers – before he even joined the race, reveal what a threat he is. He is trailing only the front-runner, former New York Mayor Rudy Giuliani. His rivals tried to poke fun at his absence from their debate in New Hampshire, but there was no doubting who had the national limelight last night.

Mr Thompson talked about his common-sense conservative principles, including low taxes, free markets, balanced budgets and the "sanctity of life".

"These principles made our country great, and we should re-dedicate ourselves to them, not abandon them," he said.

His loosely framed policies seem to impress voters less than his charm. At 6ft 6in, he stands head and shoulders above most. He can turn on the Southern charm in an instant, and likes to call the women he meets "honey" and the men "buddy". When he shows up at events, the audience are as likely to ask him to autograph their Hunt For Red October DVDs as ask him about his policies for the White House.