The race for the White House tightens after former senator Fred Thompson announced Wednesday night on a popular television show he will seek the Republican nomination for next year’s presidential race.

“I'm running for president of the United States,” Thompson said during NBC’s Tonight Show hosted by Jay Lenno.

Thompson is also an actor, best known for his role as Arthur Branch, the New York City District Attorney in the long-running television series Law & Order, aired by NBC. Shortly after he made the announcement, a formal statement offering supplementary details appeared on his campaign website.

Over the last couple of months, different speculations have appeared in the media about his potential presidential bid, but the politician who represented Tennessee in the US Senate until 2003 refrained from making his intentions official until yesterday.

Latest opinion polls indicate Thompson is very popular among voters, his popularity competing with the ones of New York City Mayor Rudy Giuliani and former Massachusetts Governor Mitt Romney.

Presidential campaigns have been launched quite early this year, but Thompson delayed his official start until September. He faces criticism from other Republican candidates for entering the race so late and failing to attend debates.

While Thompson was on Jay Lenno’s show, other candidates from the Grand Old Party (GOP) were participating at a policy debate in New Hampshire, a fact underlined by Mitt Romney.

Nevertheless, his candidacy was expected by many other Republicans, who praise him for his conservative policy which is in total contrast with a more liberal one upheld by other front runners.

Thompson will have to move fast and try to make up for lost ground, because the primary elections are closing in and he doesn’t have any more time to waste. Analysts say the 65-year-old lawyer would have to raise a considerable amount of money for his campaign in order to represent a serious competitor.