The story of the primary to date has been how one challenger after another has risen up in the polls, overtaken Romney and then fallen away through a mixture of media scrutiny and the sledgehammer of un-regulated attacks ads paid for by the slush fund loosely connected to Romney.
First there was Michelle Bachmann, the Tea Party favourite who won the opening bout when she topped the poll in the Ames Straw Poll last summer. Admittedly, the straw poll is all about paying for food and drink and getting your supporters to turn up to a state fair... (Only in America). But then she fell to earth with a crash to the extent that she scored just 6% in the actual Iowa caucuses and departed the race.
Next up was Pizza Company Exec Herman Cain. The man who wanted to be President but didn't really understand what was going on in Libya. He too became the favourite only to crash when multiple claims of sexual harrasment were made by former employees.
And then there was Rick Perry - the Governor of Texas who took 'Oh Shucks' populism to a new level. He entered the race to a huge fanfare but then fell away as the voters realised that electing someone more stupid than George W Bush would be, well, stupid.
And Newt Gingrich, the former Speaker of the House of Representatives who caused so much trouble for Clinton but who seems unable to translate that into primary success. He too saw his stock rise only to be attacked for his work as a lobbyist when he left office.
Finally there was Rick Santorum. A former senator renowned for getting pork barrel deals for his area - which is great if you are running for re-election in your state, but a little hard to explain to the voters of the other 49. In a party that is defined by religious zealotry, Senator Santorum is something special (he's more catholic than the Pope). With perfect timing he came within 8 votes of actually winning Iowa by the simple expedient of mounting his charge too late for anyone to do anything about it. The trouble is that then he became the focus of the attacks and he had no money left to rebut.
In the background the whole time have been two other candidates. Ron Paul is a 76 year old libertarian gynaecologist. His ideological purity is unimpeachable. The trouble is that his policies are hated by more than half of his party and he refuses to rule out running as a third party candidate if he loses. Paul will come second or third in every primary thanks to his fanatical band of supporters. He just doesn't have enough crossover support to win. He does have the best adverts though.
And then there is Jon Huntsman whose bid was fatally flawed by having worked for the Obama administration as Ambassador to China and by being nice. He's the other moderate in the race. But when Romney is leading by such a margin, there's no place for the other moderate. Huntsman has staked his whole run on doing well in this week's New Hampshire primary. in effect, he's this week's Santorum.
But with all the other candidates a busted flush, it has become time for the attention to focus on Romney. His problem is that he ran a venture capitalist company for a while. This business invested in other firms and hoped to make a profit. The trouble is that, when things didn't work out, people lost their jobs. And sometimes when things did work out people lost their jobs too. Today Romney made his most serious gaffe when he announced:
"I like being able to fire people"That's capitalism for you. But it sits a little uneasily in a country which is facing mass unemployment. How can the republicans attack Obama over job losses when their presumptive candidate likes sacking people? And their other main attack line - the apparently 'socialist' decision to introduce a health care safety net - is blunted too by Romney's decision to have exactly the same in Massachusetts when he was Governor.
Finally there appears to be a chink in Romney's armour. It's not enough for any of the other candidates to hope to exploit. But if it runs for a while and Romney's popularity tanks as that of the others has done then it may just be enough to see one of those waiting in the wings (Jeb Bush, Tim Pawlenty or even Sarah Palin) decide to throw their hat into the ring.