Mitt Romney suspended his bid to win the Republican presidential nomination after failing to break his rival John McCain's stranglehold on the contest.
Before entering the race, Mr Romney had a varied career as a businessman, the organiser of the 2002 Winter Olympics and governor of the state of Massachusetts.
But much of the attention he attracted during the race was the result of two factors: his religion, and his apparent switch from technocrat to social conservative.
Mr Romney is a member of the Church of Jesus Christ of Latter Day Saints - a Mormon.
Mormons say they are Christians but are regarded with suspicion by some other Christian groups, and polls have suggested that one-quarter to one-third of Americans would not vote for a Mormon for president.
Mr Romney attempted to brush off such surveys, saying that Americans might well have told pollsters they would not vote for a divorced actor for president - but they elected Ronald Reagan in two landslides.
And in a speech given a month before the first primary contests, he sought to dispel public scepticism about his Mormon faith by promising to defend religious freedom.
"If I am fortunate to become your president, I will serve no one religion, no one group, no one cause, and no one interest," he said.
"A president must serve only the common cause of the people of the United States."
Observers noted the parallel with the famous speech made by John F Kennedy during his successful campaign for president in 1960, in which he discussed his Catholic faith.
Mr Romney began his career as a businessman in Boston after completing a joint degree in law and business at Harvard University.
He is credited with helping to turn around his management consulting company, Bain & Company, when he took over as chief executive officer in 1990.
After spending the rest of the decade as head of Bain Capital, a venture-capital fund, he was asked to take charge of the Salt Lake City Olympic committee, which was mired in a corruption scandal.
Born 12 March 1947 in Detroit, Michigan
Educated at Brigham Young University and Harvard
Chair of Salt Lake City Olympic Committee, 1999-2002
Governor of Massachusetts, 2003-2007
Mr Romney moved to Utah and made a success of the 2002 Winter Olympics, positioning himself to run for governor of Massachusetts as a results-oriented pragmatist.
The 2002 governor's race was the second time Mr Romney had sought state-wide office in Massachusetts.
In 1994 he had run against the state's venerable Democratic Senator Ted Kennedy, reportedly spending more than $7m of his own money to do so.
Mr Romney lost by a 17-point margin - but that was better than any other opponent had done in any challenge to Mr Kennedy since the early 1960s.
Mr Romney was more successful in 2002, at a time when Massachusetts was facing a state budget crisis.
Again dipping into his own pockets, he spent $6.3m of his own money and took 50% of the vote to Democrat Shannon O'Brien's 45%.
Two major developments during his tenure as governor became issues during his presidential campaign: the passage of a law requiring all adults in the state to have health insurance, and a court decision requiring Massachusetts to let gay people marry.
The health-insurance law was the first of its kind in the United States, a country with no national health service.
Mr Romney was a key player in getting the law on the books, enabling him to take credit for cracking an issue that has been the subject of bitter battles for generations in the US.
He was far from supportive of the gay marriage decision, however.
His public opposition to the court-ruling marked the beginning of his recasting himself as a social conservative.
Admirers say he had always held socially conservative views, though he had appeared to back gay rights and access to abortion in the past.
Critics say his change of tune was opportunistic as he positioned himself to run for president in 2008 as the standard bearer of Christian conservatives.
Rival Senator John McCain is also widely distrusted by social conservatives.
His fundraising ability and well-organised campaigning helped catapult Mr Romney into the top ranks of Republican contenders through 2007.
But a late surge by former Arkansas Governor Mike Huckabee derailed Mr Romney's strategy in the key early voting state of Iowa.
Mr Huckabee won in Iowa, and Mr McCain won in the other crucial early voting state of New Hampshire.
Mr Romney was able to claim some success after victories in Wyoming, Michigan and Nevada.
But after Mr McCain's moderate rival Rudy Giuliani dropped out, the Arizona senator became the front-runner, and on Super Tuesday, when 21 states held Republican contests, Mr Romney was unable to dislodge Mr McCain from his position at the head of the pack.
Mr Romney, whose given first name is Willard, was born on 12 March 1947, the son of politician and auto executive George Romney.
The senior Mr Romney ran briefly for president in 1968.
Mitt Romney is married to his childhood sweetheart and has five sons.