DES MOINES — Now the race for the Republican presidential nomination begins in earnest.
Actor and former Tennessee Sen. Fred Thompson finally joined the contest Wednesday night, ending a months-long tease and giving voters a chance to see whether he can match the buildup that already has him in the top tier of public opinion polls.
As he jumped in, the rest of the field started taking shots at one another in their first post-Labor Day debate, a sign of the higher stakes as the campaign turns more intense before caucus and primary voting starts in late December or early January.
Long shots such as former Govs. James Gilmore of Virginia and Tommy Thompson of Wisconsin already have been driven from the race, and others such as Reps. Duncan Hunter of California and Tom Tancredo of Colorado battle being marginalized by their inability to muster much support.
As the candidates jostle for position, Republican voters remain split, unwilling to anoint any of nine candidates as a dominant front-runner and retaining the power to shake up the race in coming days and weeks.
"You can't call it," Republican strategist Frank Luntz said. "It's going to get shook up a little with Thompson in."
Indeed, the interest in Thompson among Republican voters signals how fluid the race remains despite the earliest campaign start in history.
Several candidates already have been campaigning for half a year, the candidates combined have spent more than $80 million and one candidate — former Massachusetts Gov. Mitt Romney — has held more than 400 events in Iowa and New Hampshire, the first two states to vote.
Still, voters haven't coalesced behind a candidate, and all of them have challenges ahead:
— Former New York Mayor Rudy Giuliani leads in national polls, but he supports abortion rights and thus remains anathema to some social conservatives. A group of 29 Republicans who watched the New Hampshire debate Wednesday night with Luntz said they were disappointed by Giuliani's performance.
— Romney leads in Iowa and New Hampshire. But he'll face his first competition soon on Iowa and New Hampshire TV, where for months he's been the only one airing ads. The focus group of New Hampshire voters also found Romney disappointing in the debate, hissing when he was forced again to explain a comment equating his sons' work on his campaign with those who serve in the military in Iraq.
— Sen. John McCain of Arizona watched his already tenuous standing erode as he supported an immigration proposal that would have given illegal immigrants a path to citizenship. But a forceful performance in the debate defending the Iraq war impressed Republican voters, suggesting that he could be poised to attempt a comeback if Republicans rally to support the recent buildup of U.S. troops in Iraq.
Thompson is the wild card, already drawing support in polls but poised either to gain if he does well in coming days — or to lose support if he disappoints.
He casts himself as an anti-abortion social conservative, a tough-on-terrorism national security conservative and a tax-cutting economic conservative. He hadn't yet fleshed out those broad values with specifics, but his star power has plenty of people ready to support him, or at least hear him out.
Making his first campaign visit as a candidate to Iowa on Thursday, Thompson quickly drew at least one socially conservative voter who'd been leaning toward Sen. Sam Brownback, R-Kan., or former Arkansas Gov. Mike Huckabee.
"Brownback and Huckabee, they're good folks, but logically I don't think they have the chance of a Giuliani or Romney," said Skip Cantwell, who makes agricultural tires for Firestone. "Thompson has the name recognition."
That didn't surprise Christopher Rants, the Republican leader in the Iowa House of Representatives and a Romney supporter.
He said he thought that Thompson could siphon support from less successful campaigns as voters started to weed out candidates who had less chance of winning and gravitate toward top-tier candidates.
But he said Romney's support was safe from poaching by Thompson. "I don't see people defecting for Fred Thompson," Rants said. "Fred's going to be a player, there's no doubt about that," Huckabee said in a conference call Thursday.
But he said that his solid social conservative credentials — he's a Baptist preacher — and the fact that Thompson once lobbied for an abortion-rights group will protect him from a loss of support to the newcomer.
Veteran conservative strategist Paul Weyrich, however, fears that Thompson will draw support from all the other conservatives, split the conservative vote and help the most socially liberal candidate in the top tier: Giuliani.
Thompson's Hollywood fame gives him a calling card that most politicians lack. But he has only so much time to show Republicans that he has a message and an ability to sell it that's better than his rivals.
"Fred Thompson has all the potential for a rapid rise in support — or a rapid collapse," Luntz said.
(Thomma reported from New Hampshire. William Douglas contributed to this article from Washington.)