By Kevin Connolly
BBC News, Washington
Mr Romney has waved goodbye to his presidential aspirations - for now
If you had to pick someone from this year's cast list of candidates to play the American president in a movie, you'd probably choose Mitt Romney.
He has the kind of telegenic good looks that create the faint impression that he might have been chiselled from a solid block of make-up.
And his long and successful business career has left him with an air of authority and the sheen of success.
But he never really connected with Republican Primary voters - one-on-one he seemed awkward and stilted, and on stage he always felt a little wooden, and lacking in conviction.
His timing was bad right to the very end.
It was one of those moments... when the agonisingly personal meets the political
He waited until he was announcing the suspension of his campaign at a Conservative political meeting in Washington to deliver what was by a mile his best speech of the campaign.
It set out the values of the modern American centre-right and ended with the conclusion: "I entered this race because I love America, and because I love America, in this time of war, I feel I must now stand aside for our party and for our country."
It was one of those moments which the slowly-unfolding gladiatorial drama of the presidential process throws up from time to time when the agonisingly personal meets the political.
Here was an audience of political insiders watching one of their own admit "I hate to lose".
But you knew that even as they listened they were all making their own calculations about what it meant for those who remain in the race.
General election focus
To deal with the most obvious point first, John McCain is now the Republican candidate.
The former Governor of Arkansas Mike Huckabee is still in there pitching, but the most he can hope to get out of it is an invitation onto the McCain ticket as candidate for the vice-presidency.
Mr McCain could do worse. Governor Huckabee is a witty and engaging campaigner who knows how to win in the Deep South and who could deliver evangelical Christians who harbour doubts about Mr McCain's conservative credentials.
In practical terms, this means that Mr McCain can start focusing his money and his energies - he is 71, don't forget - on the general election campaign to come in the autumn when he will face either Hillary Clinton or Barack Obama.
John McCain's candidacy is now without doubt - almost
The two Democratic candidates may well spend the next few months trading blows in Texas, Ohio, Pennsylvania and elsewhere.
That is politically bruising and could open wounds into which Mr McCain will be able to rub salt in due course.
But more importantly, it is expensive too - a costly primary season might drain potential Democratic Party backers in the early part of the year and make fund-raising more difficult later on.
It's worth noting, by the way, that Mr Romney was by miles the richest candidate in the race.
He was a successful businessman and venture capitalist, and the only member of the field on either side who could afford to buy airtime and pay campaign staff out of his own pocket.
Whatever outsiders might sometimes say about American politics, all that money couldn't buy the nomination, even against the notoriously cash-strapped Mr McCain.
Big on security
In political terms we can expect Mr McCain to start emphasising the huge gulf that separates him from both Democrats on the war in Iraq and the war on terror.
National security is his best issue. He was a highly-decorated pilot - and a prisoner of war - in Vietnam, and as a senator he has been an influential contributor to the national debate on anything to do with defence.
He was an early proponent of the surge strategy in Iraq, and indeed you might argue that his run for the presidency would never have taken off as it has, if that strategy hadn't proved successful.
In the end, what did for Mr Romney apart from that fatal lack of charisma was his reputation as a 'flip-flopper'
The choice facing Americans on the issue will be stark.
Mr McCain says American troops could remain in Iraq for decades after the conflict is over, as they have in Korea, Japan and Europe.
Mr Obama was against the war in the first place. And while Mrs Clinton may have voted to authorise the war - although she obviously regrets that now - she has said she would start asking for a blueprint for withdrawal on her first day in office.
A McCain candidacy means a much higher profile for the Iraq issue in general.
Mr Romney, a wealthy businessman and consultant, was better on the economy, an area where Mr McCain can seem a little shaky.
But in the end Republican voters just didn't find him convincing.
Looking for Reagan
In the final analysis, what did for Mr Romney apart from that fatal lack of charisma was his reputation as a "flip-flopper" - someone who cast off inconvenient old opinions as readily as he removed his smartly-tailored jackets at rallies to signify dynamism.
He is pro-life these days, because abortion is a touchstone issue for the Republican base.
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
But when he ran for the Senate in 1994 in liberal Massachusetts, attempting the impossible by trying to take the seat off Ted Kennedy, he said: "I believe that abortion should be safe and legal in this country."
Now theoretically there's nothing wrong with a politician who changes his mind, but to lots of Republicans this felt like a man changing his principles - and being prepared to say anything to get elected.
Which brings us to the last issue raised by Mr Romney's departure from the race - the state of Republicanism.
Essentially the GOP in 2008 is really looking for the candidate who won the presidency for them in 1980 - Ronald Reagan.
The Republican faithful trusted his instincts on all the issues that really matter to them - defence, low taxes and social policy issues like abortion.
Mike Huckabee talks heresy on some aspects of the economy: His plan to put people to work expanding freeways sounds a bit like the New Deal of the 1930s.
And Senator McCain has sounded downright liberal on issues like illegal immigration in the past.
The truth is that none of this year's crop of candidates really ticked all the boxes, but the returns from Super Tuesday indicate that Mr McCain ticks more than the others, and might tick some of the rest, given a bit of judicious prodding.
Mr Romney will be remembered as the candidate who tried a little too hard to persuade the faithful that he was with them on all the core issues when his track record suggested otherwise.
In the process, he never really found his own voice - until that speech in which he announced that it was all over.