MANCHESTER, New Hampshire (AFP) ― After his razor-thin victory in Iowa, Mitt Romney hopes a big win Tuesday in New Hampshire will set him up as the overwhelming favorite for the Republican presidential nomination.

His five main rivals are probably only vying for second place in New Hampshire, but with the frontrunner still plagued by lingering doubts over his conservative credentials and under increasing fire over his venture capitalist background, everything is still to play for in the overall race.

Here is a quick look at the six contenders for the Republican nomination to take on President Barack Obama in November 2012:

Mitt Romney

The co-founder of a Boston-based private equity firm, credited with saving the 2002 Winter Olympics in Salt Lake City from financial ruin, says he has the business acumen to turn around the faltering U.S. economy.

But Romney, 64, faced blistering attacks on the eve of the New Hampshire vote as rivals highlighted the jobs lost at firms bought by his hugely rich venture capital company, Bain Capital.

Romney has also struggled to win over staunch conservatives who look back worryingly to when he ran as a moderate to win the governorship of deeply liberal Massachusetts.

Derided by opponents as the king of flip-floppers, his Massachusetts reforms are seen as a template for “Obamacare,” the president’s health overhaul that is anathema to most Republicans.

Many conservative Christians also view his Mormon faith as either a cult or a heresy.

But all these sins may be forgiven if Republicans think he has the best chance of beating Obama in November.

Rick Santorum

Republicans with doubts about Romney’s conservatism look no further than this 53-year-old former Pennsylvania senator who was edged into second place in Iowa by just eight votes.

Liberal opponents deride him as an ultra-religious, anti-gay creationist who in the past has equated homosexuality with incest and pedophilia, but Santorum plays his social and fiscal conservatism as trump cards.

Once a long-shot, his message that the party must not compromise its core beliefs to win back the White House caught on in Iowa as did his personal working-class story, which contrasted sharply with the privileged background of multi-millionaire Romney.

Polls showed Santorum struggling to whip up the same kind of support in more liberal New Hampshire, but a place in the top three here would allow him to keep some momentum going into the next contest on Jan. 21 in South Carolina, far friendlier ground for this devout Christian conservative.

Ron Paul

The established wisdom is that this unconventional Texas congressman is too old, too radical and too far removed from Republican orthodoxy to be a viable contender for the nomination.

Try telling that to the spry, 76-year-old Paul and his wildly enthusiastic supporters, many of whom are a quarter of his age.

Paul’s legions of young fans were disappointed by his third place showing in Iowa and hope he can go at least one better here.

The libertarian-leaning lawmaker has pledged to remove U.S. troops from all overseas bases, lift sanctions on all countries ― even Cuba and Iran ― abolish the Federal Reserve, and end the war on drugs.

A survey published Sunday gave Paul 20-percent support in New Hampshire, 15 percentage points behind Romney but still a clear second.

Conservative critics say his “spoiler” candidacy is splitting the vote in a way that allows Romney a clearer route to the nomination.

The well-funded, well-organized Paul says he is in the race for the long haul and is already eyeing South Carolina.

Newt Gingrich

The former House speaker is out for revenge in a big way after his political fortunes in Iowa collapsed under a relentless barrage of negative advertisements from Romney’s camp.

Supporters of the belligerent 68-year-old political veteran are pouring millions of dollars into their own toxic ads in South Carolina, accusing Romney of having been a “predatory corporate raider” at Bain.

But time is running out for this “Reagan conservative” who sees himself as the country’s right-wing philosopher king and he must hope for at least a third-place finish here to show some momentum in the race.

In the 1980s the young upstart led conservative Republicans against their own party establishment, while sowing partisan politics with hard-edged attacks on Democrats.

His masterstroke was “Contract for America,” a comprehensive reform plan that helped Republicans recapture the House in the 1994 elections and led to Gingrich’s elevation to speaker.

However, the triumph was short-lived and Gingrich stepped down in 1998 after a tenure marked by infighting, gridlock and government shutdowns.

Rick Perry

The tough-talking Texas governor answered the prayers of core Republicans when he entered the race in August, vaulting to the front of the pack as the ultimate non-Romney candidate.

But the photogenic 61-year-old Air Force veteran with a thick crop of dark hair came unstuck in the debates, displaying a weak grasp of policy and making a series of embarrassing gaffes.

Perry appeared to put the final nail in his campaign’s coffin in mid-November when he forgot a crucial part of his stump speech and stammered for an agonizing 53 seconds.

The states’ rights champion named the departments of commerce and education as targets for elimination but could not come up with the third, the energy department.

“The third one, I can’t, I’m sorry, I can’t. Oops,” he concluded.

Jon Huntsman

This former Utah governor, who was Obama’s envoy in Beijing before entering the race, gave up on Iowa, placing all his bets on New Hampshire.

“They pick corn in Iowa. They actually pick presidents here in New Hampshire,” the second Mormon in the race opined.

Huntsman, 51, gambled that if he could somehow win or come in a strong second in New Hampshire, he could revive a lackluster bid dogged by his perceived closeness to Obama.

Despite impressive foreign policy credentials and a dramatic campaign launch in June at the Statue of Liberty, his campaign has not caught on with Republican voters.

Opinion polls showed him making some headway in the run-up to Tuesday’s vote, but without a strong showing it must be the end of the road for his candidacy.