The list of candidates in the race to win the Republican Party's nomination for U.S. president has thinned considerably after just one caucus (Iowa) and one primary (New Hampshire).

The current front-runner is businessman and former Massachusetts governor Mitt Romney. Romney won in New Hampshire and finished a close second to Rick Santorum in Iowa in what Romney's campaign called a virtual tie (although the Republican Party said a winner could not be declared because of lost ballots from several precincts). Public opinion polls have him in front to face-off against Barack Obama in November, who will be seeking a second term in the White House.

Here's a list of the candidates still in the Republican race, followed by a list of candidates who have dropped out or were once considered possible contenders.

Who's in:

Mitt Romney: He officially announced his candidacy on June 2, 2011, and is the one to beat. The former Massachusetts governor spent millions of dollars from his own fortune to run in the 2008 presidential race but had a lacklustre campaign and lost the nomination to John McCain. Romney very much looks like a president, or at least the Hollywood version of a president, and has the CEO pedigree to be taken seriously on the economy. But his opponents and critics have attacked his reversals on abortion, his Mormon background, his "vulture capitalism" and his own state-run health-care plan as governor — already dubbed "Romney-care" — as reasons why he shouldn't be the conservative standard bearer.

For his part, right from his kick-off speech, Romney has been lambasting the president's management of the economy, lamenting the increase in the U.S. "misery index" under the current administration and promising to repeal Obama's health-care law.

Newt Gingrich: Arguably, the best-known of the top-tier contenders, Gingrich gained fame after a series of fiscal standoffs with president Bill Clinton when Gingrich was the Republican House Speaker in the 1990s. The main proponent of the Republicans' 1994 "Contract with America," the former Georgia representative hasn't held an elected position in more than a decade.

But he has stayed in the public eye through on-air stints as a Fox News Network commentator and author. He's been raising a ton of money and spreading the word on Facebook and Twitter, where he formally announced his candidacy for 2012. Still, with two previous marriages and confessions of infidelity of his own, Gingrich's baggage could convince social conservatives to stay home rather than vote for him.

Rick Santorum: The former Pennsylvania senator and ex-Fox News contributor came out swinging when he declared his candidacy on June 6, 2011, saying Obama's health-care bill threatened to undermine individual freedoms by removing people's power to choose their own plan. "Every single American will be hooked to the government with an IV," Santorum said. "They want to hook you. They don't want to free you." Santorum, already highly popular with social conservatives for his opposition to abortion rights, accused Obama of devaluing America's "moral currency" by supporting federal abortion funding and halting the federal government's defence of a federal law that banned recognition of same-sex marriage.

Ron Paul: The Texas congressman and 2008 also-ran announced his candidacy on May 13, 2011. Nicknamed "Dr. No" in reference to his opposition to government spending, he's also a foreign policy isolationist, which puts him at odds with the Republican party, especially its neo-conservative wing. While some polls ranked him closest to taking down Obama in a head-to-head matchup, critics say his social and isolationist views will prevent him from getting the chance.

Buddy Roemer: Roemer served four terms in Congress in the 1980s as a Democratic representative from Louisiana, moved to the state governor's mansion in 1988 and then switched to the Republican Party in 1991 but lost the party's gubernatorial primary. After 20 years in business, most recently as a bank executive, Roemer declared his candidacy for president on July 21, 2011. He finished seventh in the New Hampshire primary.

Fred Karger: Fred Who? Actually, that's his slogan, or one of them. A retired Republican strategist who worked on the campaigns of Ronald Reagan and George H.W. Bush, Karger has already made history by being the first openly gay candidate to register for the presidency. If allowed into Republican debates, look for Karger to be a thorn in the side of Mitt Romney, as he's already declared the goal of his campaign is to "expose" what he says is the intolerance of the Mormon faith.

(Another 20 or so candidates who have not announced their withdrawal received votes in the New Hampshire primary.)

Who's out:

RIck Perry: The Texas governor galvanized the Republican race by announcing his presidential bid in Charleston, S.C. on Aug. 13 — the same day the existing candidates were taking part in a straw poll in Iowa. Another champion of low, low taxes and small government, this social conservative is also a naysayer on the issues of gay marriage and abortion, while his ready deployment of firearms — like the time he used a laser-sighted handgun to kill a coyote while out for a jog with his dog — would make Charlton Heston proud. Although once considered a frontrunner, Perry faded and dropped out of the race on Jan. 19, shortly before the South Carolina primary.

Jon Huntsman: He served as governor of Utah from 2005 to 2009, and more recently, was the U.S. ambassador to China before joining the race on June 21. Like Romney, Huntsman is a Mormon, although he says he is more "spiritual" than religious. While governor of Utah, Huntsman gained a reputation as an effective tax cutter, such that the Pew Center named Utah the best managed state. On Jan. 16, Huntsman bowed out of the race, putting his support behind Romney.

Michele Bachmann: The congresswoman and former tax lawyer from Minnesota was the only woman in the race, and despite some high-profile gaffes, became a Tea Party favourite. Bachmann gave a feisty performance in the first debate of Republican presidential aspirants on June 13, where she espoused her conservative values and confidently derided Obama as a "one-term president" running a "gangster government." She dropped out of the race on Jan. 4, after placing last in the Iowa caucus.

Gary Johnson: A former governor of New Mexico, he is not well known outside his state and doesn't hide his libertarian views, which include his support for same-sex unions and the legalization of marijuana. His fiscal conservatism and rejection of state spending bills between 1995 and 2003 earned him the nickname "Governor Veto"  and he says, "America needs a 'President Veto' right now." On Dec. 28, 2011, Johnson withdrew from the race.

Herman Cain: A conservative talk show host and the former CEO of Godfather's Pizza, Cain announced his presidential bid on May 21 but suspended his campaign on Dec. 3, following allegations of sexual harassment and an extra-marital affair. While campaigning, he appeared to relish people writing him off as a no-hope candidate. "I wasn't supposed to succeed in climbing the corporate ladder in corporate America," he told CNN in January. "So to the people who say I don't have a chance, I say, thank you. Because that inspires me."

Thaddeus McCotter: The Michigan Congressman officially ended his presidential bid on Sept. 22, 2011.

Tim Pawlenty: The former Minnesota governor was on the vice-presidential short list for McCain's 2008 campaign. He ended his campaign on Aug. 14, 2011.

Who might have run:

Sarah Palin: You know who she is. Everybody does. That's the point. It helps to ask people to vote for you without having to tell them your name. The self-described "Mamma Grizzly" was making all the stops and giving all the signs she's interested. Near-worshipped by the Tea Party movement, the former Alaska governor and 2008 Republican vice-presidential candidate might have had enough populist appeal to wrestle the party's establishment and noogie it into submission, while bringing the grassroots along. Her Republican critics feared she could take them all right off a cliff in an election. In the end, however, she announced Oct. 5 that she wouldn't play. Instead, she told supporters, she and her husband Todd would "devote ourselves to God, family and country." What that meant, of course, remained to be seen.

Chris Christie: Another name ranked among the highest in polls on a hypothetical Republican race, the New Jersey governor has earned a reputation for slashing government spending and taking on unions since being elected in 2009. He said on several occasions that he will not be seeking the Republican nomination, and yet many conservatives held out hope that he'd reconsider. But Christie ended the speculation at a press conference on Oct. 4, 2011 in Trenton, N.J., when he said that entering the race for the party's nomination "just didn't feel right." He told reporters that "now is not my time" to run for the White House, and added that he's committed to fixing a state he called "pretty messed up."

Jeb Bush: A popular former governor of Florida and the younger brother of former president George W. Bush, Jeb says he has no plans to run for the big job.

Mitch Daniels: Indiana's current governor and a former budget director under George W. Bush, Daniels announced May 22, 2011 that he would not stand for the Republican nomination. 

Mike Huckabee: The former Arkansas governor and 2008 contender is a favourite among social conservatives and led polls among the Republican field, even though he hadn't launched an exploratory committee. Huckabee's stayed in the limelight through radio and TV hosting duties on Fox News, as well as a recent book tour. But in mid-May he announced that he'd be sitting this race out.

Donald Trump: His decision in May not to jump into the race — even though he said he thought he could win the presidency — came after a PR implosion, in which he championed the "birther" movement against Obama and dropped the MF-bomb on the Chinese in his call for a trade war. The Republican establishment press ridiculed his rumoured candidacy, while former Bush strategist Karl Rove called him a "joke" candidate.

Marco Rubio: Considered a rising star in the GOP and the apparent favourite of incendiary talk-show host Rush Limbaugh, the rookie Florida senator has gained many supporters. Although a Tea Party favourite during his Senate run, he has rankled some in the movement after declining to join a Tea Party caucus, and has ruled out a run for the presidency.

Rudy Giuliani: Wow, did his campaign not click last time. Giuliani entered the 2008 race a heavy favourite — bolstered by his nationwide approval as New York's mayor during the Sept, 11, 2001, attacks. But Rudy quickly wilted as a frontrunner, fading fast in the primaries, and eventually threw his support behind close friend John McCain. He acknowledges he would be a long shot but has been keeping his name alive.

Rand Paul: The son of Ron Paul and an ophthalmologist-turned-politician, this Tea Party member's star began rising with his Senate victory in Kentucky in the November 2010 midterm elections. He has followed his father's path in calling for much less government spending.

Paul Ryan: Another rising star who many among the Republican ranks are urging to run. A fiscal hawk, and vocal critic of Obama's health-care legislation, the Wisconsin congressmen's stature has continued to grow in the party. One sign: he was asked to deliver the GOP response to Obama's State of the Union Address. Chair of the House Budget Committee, his plan to tackle the deficit and reform Medicare and Medicaid gained praise among conservatives, but was slammed by Democrats. He says he has ruled out a presidential bid, but appears to be open to the vice-presidential job.