"I think it is too late for someone to mount a credible campaign," Jowers said, noting Romney, Giuliani and McCain already have considerable campaign resources available, something that Thompson will only begin building. "He has a Herculean task ahead of him."

Money may determine how long Thompson lasts.

Kelly Patterson, director of Brigham Young University's Center for the Study of Elections and Democracy, said that while Thompson will benefit from what Patterson characterized as his "freshness as a candidate," the other major contenders have already raised record amounts of money in record time, thanks to the unique nature of the 2008 campaign cycle.

With the presidency up for grabs, "the intense nature of this cycle early on has forced the hand of fund-raisers, party activists and political consultants" to choose a candidate. Romney, for example, bested his Republican competitors by raising more than $21 million in the first three months of the year.

"In some ways, it's an arms race," Patterson said. "Because the fields are so crowded, the candidates believe they have to differentiate themselves. ... The way they do that is by committing major talent, raising large sums of money and doing well" in events such as today's debate.

Opportunity knocks

Thompson's looming announcement puts extra emphasis on tonight's debate, said Matt Eventoff, a political communication and public speaking expert.

"If a top-tier candidate does stumble, it could lead to a media barrage that removes him from the first tier, as the press knows a third top-tier candidate is on the way," Eventoff said. "In the same vein, if a candidate puts in an outstanding performance, that candidate solidifies his place in the top tier. Thompson has a very distinct advantage as he does not have to participate in the debate and knows he will be a top-tier candidate upon declaring."

Patterson said there's no question that Thompson should be taken seriously, despite his late entry in the race.

"He has a high profile in the national media. He's an experienced candidate. He can raise funds initially," Patterson said. And with many Republicans clamoring for another choice, "he's the one who can capitalize on that. ... The question is, can he make the best of this opportunity?"

Romney spokesman Kevin Madden said Thompson is a formidable candidate, but as Romney meets with more and more voters the campaign feels "very good" that there is growing support among Republicans.

"We welcome anyone into the race," Madden said.

Thompson on 'Hannity'

MANCHESTER, N.H. — Former Sen. Fred Thompson, who has all but declared his candidacy for president, may not be on the stage at tonight's Republican debate in New Hampshire, but he will have another platform all to himself — on the Fox News Channel.

NYTimes.com reported Monday that Thompson is to appear live on "Hannity & Colmes" after the debate.

This show may be an even better venue for Thompson. He will have the set to himself and will not have to compete with his 10 soon-to-be rivals for precious airtime during the two-hour talk-fest.

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