Michele Bachmann was out, Rick Perry was back and Rick Santorum was up in the most volatile Republican presidential nominating contest in decades on Wednesday, as conservative Republicans searched for an alternative to frontrunner Mitt Romney.

Bachmann, a U.S. congresswoman from Minnesota, stepped down after a dismal sixth place finish in the first Republican nominating contest in Iowa, which was decided by a margin of 8 votes out of the 122,000 cast.

Perry, the governor of Texas, stayed in the race despite earlier hinting he would drop out.

Frustrated at conservatives' failure to unite behind a single candidate, Christian conservative leaders planned a Texas meeting this weekend to thrash out strategy.

Their candidate may turn out to be Santorum, a former U.S. senator from Pennsylvania, who came a close second to Romney in Tuesday's Republican Iowa vote, which kicked off the 2012 presidential election cycle.

Santorum swept into New Hampshire buoyed by the Iowa result. His campaign said he had raised $1 million in the last 24 hours.

Santorum told Fox News' The O'Reilly Factor that we're going to do surprisingly well in New Hampshire. We're going to be a much bigger player than everybody anticipates.

A CNN poll showed Santorum doubling his support to 10 percent in New Hampshire, although he remained far behind Romney, a former governor of neighboring Massachusetts.

Distrusted by conservatives, Romney has struggled to break above the 25-percent level in national polls of Republicans in the race to choose a challenger to President Barack Obama for November's presidential election.

He has a solid campaign infrastructure and is favoured to easily win the January 10 New Hampshire primary. Romney picked up the endorsement of Senator John McCain, who was the party's nominee in 2008.

I'm really here for one reason and one reason only, and that is that we make Mitt Romney the next president of the United States of America, McCain said at a rally in Manchester, New Hampshire. And New Hampshire is the state that will catapult him on to victory in a very short period of time.

SANTORUM'S PROBLEMS

An afterthought in the race until now, Santorum could have difficulty scaling up his campaign to compete in other states. On Wednesday, his website apparently crashed under a deluge of traffic.

Santorum has escaped close scrutiny so far, but rivals have plenty to work with if they want to attack him as a Washington insider at a time when anti-government anger is running high. As a congressional leader, Santorum led an effort to link Republicans closely with lobbying interests before voters threw him out of office by an 18-point margin in 2006.

His career out of public office could come under attack as well: his million-dollar-plus income in 2010 included substantial payments from a lobbying firm and a hospital group that was hit with two lawsuits for allegedly defrauding the federal government.

Conservative voters have boosted nearly every other candidate in the race to the top of opinion polls over the past six months.

Another hopeful who has seen his support crumble, Perry decided to stay in the race after earlier saying he would reassess his campaign after a fifth-place finish in Iowa.

We are going to go into places where they have actual primaries and there are going to be real Republicans voting, Perry told reporters, referring to New Hampshire and South Carolina.

The unsettled nomination race - which pollster Gallup said was the most topsy-turvy in 50 years - also leaves an opening for former House of Representatives Speaker Newt Gingrich or Perry if Romney can't connect with more voters.

South Carolina's January 21 primary is shaping up to be a crucial test.

Iowa picks corn, New Hampshire picks campaigns' pockets and South Carolina picks Republican presidents, and it is far from settled in South Carolina, former state Republican Party chairman Katon Dawson, a Perry supporter, told Reuters.

Perry, a steady leader in the money stakes, has $3-4 million on hand to fund a multi-state campaign, according to a knowledgeable source.

Gingrich, who led opinion polls in December on the strength of his television debate performances, can look forward to two more debates on Saturday and Sunday in New Hampshire as he tries to return to the top tier.

At the end of September, Romney's campaign had $14.7 million cash on hand while Santorum's had $189,556, according to the candidates' Federal Election Commission filings.

Romney can also point to the support of prominent leaders like South Carolina Governor Nikki Haley and McCain.

Opinion polls show that Romney would fare best among the Republican candidates in a head-to-head matchup against Obama.

Still, he has yet to show that he can win the support of more than one in four Republican voters. His 25 percent showing in Iowa matched his 2008 vote total, and he has barely cracked that ceiling in national opinion polls.

If Mitt wants to wrap this nomination up he has to get beyond establishment Republicans, said Republican strategist Ford O'Connell.

Undecided New Hampshire voter Karen Eastman said she was not swayed by the Iowa results.

I think every state is different, so you really can't go by what happens (in Iowa), said Eastman, a 53-year-old seamstress.

Once they get in office a lot of them don't do what they say they're going to do. It's really hard to vote for anybody nowadays, it really is, because they don't mean what they say.

The volatility of the race may be good news for Obama, who is building a huge fundraising and vote-getting organization for the November general election. His poll numbers are improving as the unemployment rate, now 8.6 percent, declines.

Obama has won some tactical victories in Washington in recent months by taking a harder stand against Republicans in Congress.

On Wednesday, he said he would bypass Congress and install his picks to head a new consumer financial watchdog agency and serve on the National Labor Relations Board. Liberal advocacy groups cheered the move. Republicans, who had blocked the appointments in the Senate, questioned its legality.

(Additional reporting by Patricia Zengerle in Washington, Scott Malone in New Hampshire, Jane Sutton and Steve Holland in Iowa and Karen Brooks in Texas, Writing by Andy Sullivan, Editing by Alistair Bell and Christopher Wilson)