DES MOINES -- One Republican presidential candidate is well-known, the other remains a question mark.

One has the backing of several big-name Iowa GOP activists and, by all accounts, has constructed a respectable statewide organization. The other has yet to officially announce his candidacy, plug in a phone or even set foot in Iowa.

But if you believe a series of recent opinion polls, one is steadily sinking while the other is steadily rising.

Arizona Sen. John McCains mounting list of troubles and former Tennessee Sen. Fred Thompson's rapid ascent are two of the biggest stories shaping the race to win Iowas Republican caucuses. And they've proven that conventional wisdom can be as fleeting and fluid as a cable TV news ticker.

At one time McCain was among the top contenders in Iowa, and Thompson was still a fictional district attorney on TV's "Law and Order." Now Iowans are abruptly tuning out McCain just as they're eagerly tuning in to learn more about Thompson's potential.

"People are holding their breath and waiting for Mr. Thompson to arrive on the scene and see how he starts his campaign," said Don Kass, a Plymouth County farmer and local Republican Party chair.

McCain carries baggage

And while Thompson is the campaign's newest flavor, McCain is a veteran scarred by politics past and present.

Iowa Republicans say McCains biggest current problem is the failed immigration reform effort he co-sponsored. The bill, which offered both beefed up border security and a path to citizenship for millions of illegal workers, infuriated a broad swath of GOP conservatives who saw it as amnesty for criminals.

"I just think McCain has been really hurt by this immigration thing," said Eric Kruse, a real estate appraiser from Allison who chairs the Butler County Republican Party. He said McCain is sinking in his area despite having a good local staff and organization.

"That's not the problem," Kruse said.

Across the state in northwest Iowa, Kass said immigration is a huge issue.

"That seems to be all anybody can talk about," said Kass, who is staying neutral in the caucus race, for now. "McCain hasn't done himself a lot of good with his stand on immigration. I even talked to one of his fervent supporters and asked if this bothered him. He said yes it does."

Some Iowa Republicans fired up by immigration were already wary of McCain, who snubbed Iowa's caucuses when he ran for president in 2000. He's also identified with campaign finance reforms disliked by many Republicans, a controversial compromise with Democrats on GOP judicial appointments and his previous criticism of ethanol subsidies. He now sings the corn-based fuels praises.

In mid-June McCain followed the lead of former New York governor Rudy Giuliani and announced that he would skip the Iowa GOP's August straw poll. The decision didn't sit will with some Republicans.

McCain held a fund-raiser last year for State Rep. Doug Struyk, R-Council Bluffs, who also served on the senator's Iowa PAC committee. But Struyk is now backing former Massachusetts governor Mitt Romney. Romney is considered the favorite to win Iowa's caucuses.

"I'm partial to somebody that's been in an executive position," Struyk said explaining his support for Romney. He insists Iowans are looking for a candidate who is not tied to an unpopular Congress.

McCain's Iowa campaign chairman, veteran GOP strategist Dave Roederer, argues that the senator's Iowa organization is strong enough to weather what he sees as temporary turbulence. His top strategists include well-regarded veterans such as former state GOP chairman Chuck Larson Jr. and Iowans for Tax Relief Executive Director Ed Failor Jr.

McCain's most loyal Iowa supporters -- including local mayors and military veterans -- are sticking by their candidate.

"I just appreciate his candor and his honesty. I know those are clichés, but I do like the guy," said Clear Lake Mayor Nelson Crabb. "And I'll hang with him as long as he's there."

State Rep. Bill Schickel, R-Mason City, said McCain deserves credit, not criticism, for tackling tough issues such as immigration. He believes Iowa GOP voters will eventually give him that credit.

"I think that Sen. McCain is one of the rare political figures that puts America ahead of himself. Because of that he's an underdog right now, no doubt about it," Schickel said.

Thompson draws interest

Kruse, the GOP chairman in Butler County, said he was surprised last week when one-fourth of county fairgoers who filled out slips of paper in an unscientific straw poll picked Fred Thompson. He finished second behind Romney and far ahead of Giuliani and McCain.

"I think the Republicans are looking for a little star power," Kruse said. "That could fade or it could increase, depending on what kind of campaign he runs."

For some Iowans, Thompson is an attractive but unfamiliar possibility.

"I'm kind of one of those who is waiting for somebody else, maybe," said Joe Van Ginkel, GOP chairman in Madison County. "The problem is I don't watch prime-time TV. So I have no idea who Thompson is."

Thompson has yet to introduce himself to Iowans. It's uncertain when he will plunge into the caucus race, although he's climbed steadily in a string of polls in Iowa without getting his uniform dirty.

"For all the people who said he's got to get in, he's got to get in, 75 percent of the same people are now calling me and saying, 'Man, he ought to just stay out as long as he can,'" said Mark Corallo, spokesman for Thompson's exploratory committee.

If he runs, Corallo said Thompson will campaign frequently in Iowa. The Tennessean has not decided whether he'll compete in the straw poll, but so far hes made no preparations to take part.

Corallo insists that many of the hundreds of calls and e-mails his office receives every day urging Thompson to run are from Iowa Republicans.

"It's been kind of amazing. In all my years in politics and government I've never seen anything like this," Corallo said. "Maybe we should take a new look at how to campaign for national office."

But Iowa Republican leaders insist that Iowans' patience could wear thin if Thompson doesn't make a decision soon and do some old-fashioned campaigning here.

Contact Todd Dorman at (515) 243-0138 or at todd.dorman@lee.net