WASHINGTON — The Republican White House race has sharpened into a three-way brawl, pitting a moderate businessman and a Tea Party firebrand against a Texas governor promising the best of both worlds.

For months, former Massachusetts governor Mitt Romney has led the polls despite conservative misgivings about his history of governing from the middle and his state health care overhaul that inspired "Obamacare."

But now he faces a major challenge from ultraconservative congresswoman Michele Bachmann, who rode a Tea Party wave to victory in Iowa's Ames Straw Poll -- seen as a key test ahead of early nominating battles.

And both could face a major challenge in longtime Texas Governor Rick Perry, a social and fiscal conservative with a strong record on the economy, whose entry into the race on Saturday rained on Bachmann's Iowa parade.

Perry, a small government champion and social conservative who held a 30,000-strong prayer rally this month, can go head-to-head with Bachmann in winning over the US right wing and tout more governing experience than Romney.

"He brings to the table the possibility of winning, that Bachmann does not, in a general election," said Larry Sabato, a professor who heads the University of Virginia's Center for Politics.

"Romney has serious problems with the Tea Party and with the most conservative elements in the Republican Party, and Perry has their support."

Perry, whose state has led the country in creating jobs in recent years despite high national unemployment, is also a formidable campaigner who has won three elections since succeeding George W. Bush in 2000.

"He's going to go right after Romney, and I don't know that Romney is fully prepared for the way that Perry campaigns," Sabato said.

"Perry has had a scorched-earth philosophy for a long time and that is how he has stayed in office as long as he has."

Romney, on the other hand, has had a months-long jump-start in winning over the establishment and crucial fund raisers, and has experience in running a national campaign from his failed 2008 bid for the Republican nod.

"(Perry is) untested, and although we have reports out of Texas that he's a strong campaigner, you really test your mettle on the national stage," said David Corbin, a politics professor at New York's King's College.

Romney and Bachmann could also hone in on Perry's more than two decades in state government to try to paint him as a career politician with little experience in the private sector or among ordinary citizens.

"If (Bachmann is) going to play an angle, I think it will be the angle that if you don't like Washington, DC and you don't like government so much, then why have you spent your life in government," Corbin said.

With her straw poll win, Bachmann also appears to be in prime position to win the Iowa caucus in February, a crucial early contest that could provide a major shot of momentum.

"Bachmann demonstrated she can pull together a ground game and appeal to an important segment of the electorate that includes Tea Partyers, social conservatives and home-schoolers," Washington Post conservative columnist Jennifer Rubin wrote after the poll results.

"She's the favorite to win the Iowa caucuses next year in a state that has proven tailor-made for her."

But while she has proven skilled at turning out the party's activist base -- less than 17,000 people voted in the nonbinding Iowa poll -- she may have to tack to the center to prove she can take on Obama in a general election.

"Her competition is getting stiffer and she'll need to expand her appeal," Rubin wrote.

With six months to go before the first nomination vote, there is still plenty of time for another candidate to shake up the race, and conservative celebrities like Sarah Palin and Rudy Giuliani are still hinting at runs.

Congressman Ron Paul -- a champion of small government and fierce opponent of foreign interventions -- came in a close second in Iowa and can count on a small but highly dedicated group of supporters to keep his campaign alive.

"The Ron Paul folks have been stronger this year, more organized, and if he can go from being what you might call a Star Trek candidate to a real candidate... he may stay in there," Corbin said.

"It really is easy to discount him because he isn't fluid on stage, he does not seem presidential, but he does have the ideas and he has a great group of supporters... That support shows itself in the early states."