SUPPORTERS of the television star and former senator Fred Thompson are urging him to jump into the White House race quickly to maintain the momentum of his unofficial campaign for the 2008 Republican nomination.

Aides say an announcement is imminent but are discounting speculation that it will be on or around July 4, Independence Day.

A formal declaration will mark the moment of truth when the 64-year-old former senator for Tennessee and star of the television series Law & Order will have to prove whether he can live up to his early shine.

The tall, baritone-voiced Thompson is mobbed by “Fredheads” wherever he appears and is now assembling a well-regarded political team and fundraising operation.

He has been rocketing up the polls to within a few points of the early frontrunner Rudy Giuliani, the former mayor of New York, but is beginning to face a barrage of negative attacks from Democrats and may have got as far as he can on sheer star power.

Thompson aide Dan Hughes, a former organiser for Ronald Reagan in the key primary state of New Hampshire, said: “If he says go, we’ll go and we’ll probably win the state for him, but we definitely need the go-ahead. He has to declare.”

The actor teased supporters last week with visits to Nashville, Tennessee, where he intends to set up his campaign headquarters, South Carolina – a potential bastion of support for him in the South – and New Hampshire.

“I plan on seeing a whole lot more of you. How about that?” he told a packed reception for Republicans in New Hampshire.

It was their first glimpse of him and his wife Jeri, 40, who was wearing a modest black skirt and high-necked sleeveless top. She won over activists, who confided that they had been concerned about her racy image.

“I was very relieved,” said one Fredhead. “I’d seen the pictures of her in a low-cut dress, but she looked like a first lady.”

So far, Republicans believe Thompson has run a remarkably nimble, nontraditional campaign that has made the most of the internet and YouTube to rally fans at no cost. He poses a formidable challenge to Democrats in the South, where Hillary Clinton is likely to struggle for votes, and in the Rocky Mountain states, which turned Democrat at the last congressional elections, but where mistrust of East Coast liberals runs deep.

Thompson’s visit to Baroness Thatcher in London 11 days ago is being hailed as a masterstroke, boosting his credentials as a new Reagan with a hard-nosed, tough-on-terror foreign policy and an interest in preserving the special relationship with Britain.

Thompson told The Sunday Times the former prime minister was “wonderful”, but it also appears she was in a bossy mood. “She told me where to stand and which way to turn - it was totally delightful,” he said.

He was referring to the moment when they stepped outside her office for photographs, but there was a hint the Iron Lady may have also been giving him political directions.

Thompson is not the only 2008 candidate seeking to inherit Reagan’s mantle, but he is doing a better job than most, according to Marlin Fitzwater, Reagan’s White House spokesman, who was at the New Hampshire party.

“There are a lot of similarities,” he said. “President Reagan used to take a lot of kidding for being an actor but he used to say I don’t know how you can do this job without being an actor.”

Some Republicans fear Thompson lacks Reagan’s substance and staying power, however. The former president served first as governor of California, America’s most populous state, whereas Thompson spent eight years in the Senate, which is regarded by some as little more than a talking shop.

According to Republican sources, Thompson passed up an offer to run for governor of Tennessee, which would have entailed onerous duties such as shoring up the state budget and fixing its ailing healthcare system.

In New Hampshire, Thompson made a speech designed to appeal to the Republican base, but while it was big on “common sense”, one of his favourite phrases, it was short on specifics.

“He stands for oxygen, motherhood and apple pie so long as it doesn’t disrupt your digestive system,” said Nicholas Sanchez, a professional fundraiser, who predicted Thompson’s campaign would fizzle.

Bill Frist, the former Republican leader of the Senate and a key Thompson supporter in Tennessee, questioned his friend’s appetite for the job last week. “Does he really have the passion, the energy, the fire in the belly to run? I believe that he does, but we will only know as he gets on the campaign trail.”

The Democrats intend to exploit Thompson’s reputation for indolence. “He has the advantage of name recognition and, unlike the other candidates, he doesn’t carry a lot of baggage,” said Leon Panetta, former White House chief of staff under President Bill Clinton. “But during his time in the Senate, he didn’t accomplish much.”

Panetta also doubts the actor has Reagan’s personal strengths. “He doesn’t have Ronald Reagan’s smile and friendly approach. He’s played dour roles in the movies. He’s often the bad guy or the grumpy guy.”

In the 1993 film Born Yesterday, starring Melanie Griffith, Thompson was said by critics to have given one of his most “convincing” performances as a “sad, corrupted” senator. Although nobody doubts his personal integrity, he is being tarred for his work as a lobbyist for controversial causes.

Thompson achieved fame when he came to Washington as a young lawyer during the Water-gate hearings in the 1970s. His persistent questioning revealed the existence of the notorious Nixon tapes. But he went on to forge a lucrative career as a lobbyist for more than 20 years and now lives in a $3m home in the same street in McLean, Virginia, as Colin Powell, the former secretary of state.

In the past three years, he has earned $750,000 lobbying for Equitas, a British company that handles billions of dollars’ worth of asbestos claims for Lloyd’s of London, while also playing district attorney Arthur Branch in Law & Order.

Among his other clients were Jean-Bertrand Aristide, the deposed leader of Haiti, and a company lobbying for an experimental nuclear reactor, which was later cancelled at a cost of $1.7 billion to taxpayers.

Thompson rebuffed the accusations with characteristic good humour. “I’d just say, ‘Keep it up, guys.’ These are the same things you tried back in the 1994 campaign when I first ran [for the Senate] and you got within 20 points of me.” Hillary Clinton may not be able to make the most of these attacks because of her ties to lobbyists in her own campaign. “There isn’t a candidate in Washington who doesn’t have their own connection to lobbyists,” Panetta said.

Unlike other Democratic presidential candidates, Clinton would also find it difficult to score points against Thompson for championing Lewis “Scooter” Libby, Vice-President Dick Cheney’s former aide, who has been convicted of perjury over the outing of a CIA officer.

Thompson is a high-profile supporter of Libby’s legal defence fund and is calling on President George W Bush to pardon him. It is uncomfortable territory for Clinton, given her husband’s pardon for Marc Rich, a fugitive financier, whose former wife is a prominent Clinton donor.

The latest polls show Clinton racing ahead for the Democratic nomination, but failing to take Republicans and independent voters with her. A Mason-Dixon poll last week revealed 52% of respondents would refuse to vote for her as president. She was the only candidate of any party to have a majority of the electorate against her.

A critical test of the candidates’ strength will come when they reveal their fundraising figures for the second quarter of the year, which ended yesterday.

Clinton is said to be on target for a record-breaking haul of $27m, but Barack Obama, her main rival, is expected to have kept pace with her. Money is pouring in for Thompson, while it is drying up for John McCain, the Republican senator for Arizona.

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