WASHINGTON — The GOP presidential race can be summed up this way: three strong contenders and a hunger for someone else.

"There's no question that there's a very open field," said Ken Mehlman, a former Republican National Committee chairman. Unlike in 1980, 1988, 1996 and 2000, "there's not a presumptive front-runner," he added.

The nomination fight has become even more fluid since the year began, which is unusual for a party that typically has a clear heir apparent.

For now, former New York City Mayor Rudy Giuliani has the lead in national popularity polls. Ex-Massachusetts Gov. Mitt Romney has the most money. Arizona Sen. John McCain may have the superior national political operation.

But none has a clear advantage in all three areas — polling, fund-raising and organization — that are traditional measures in determining which candidate is in the best position to become the nominee. Perhaps more telling, Republicans say, is that none has articulated a message or offered an agenda that a majority of the party supports.

"What's missing so far is a clear down-the-line conservative champion, an establishment candidate," said Greg Mueller, a GOP consultant.

Nine months before the leadoff Iowa caucuses, the fragmented field and disenchantment with the top candidates may present an opportunity for a fourth formidable contender to emerge.

That could be an underdog such as Sen. Sam Brownback of Kansas or two former governors — Mike Huckabee of Arkansas or Tommy Thompson of Wisconsin.

Other prominent Republicans are flirting with a run, including former House Speaker Newt Gingrich, and could shake up the field. The latest to express interest is Fred Thompson, the actor and former Tennessee senator who, friends say, is seriously considering a bid. He is running third in a few national polls without doing anything more than acknowledging he was thinking about running.

Such buzz is evidence of the degree to which GOP voters are seeking alternatives to Giuliani, Romney and McCain. Conservatives who dominate the Republican primary see all as flawed.

In Iowa, Susan and Roger Rowland of West Des Moines are attending campaign events to find someone to embrace. Last week, they saw Giuliani one night and Romney the next. But they were not impressed enough by either to commit. They have not seen McCain and are open to learning more about others, too.

"There are a lot of candidates out there, but I don't really know what I'm looking for," Susan Rowland said, sighing. Her husband said, "If I had to pick today, I'd probably pick Romney, but I'm really glad I don't have to pick today."