A week is a long time in politics, Harold Wilson once observed at the end of a bad week, and the remark was considered so brilliantly penetrating that it was immediately entered into the Oxford Book of Quotations. As he prepares for his second presidential debate tomorrow, Barack Obama knows exactly what the British Labour prime minister meant.
On the day of the last debate on October 3, the President appeared to be in an unassailable political position. Holding comfortable leads over his Republican rival in several battleground states, Obama was the clear favourite to win the November 6 election.
Meanwhile, Mitt Romney was living on borrowed time, bedevilled by a series of gaffes and missteps, derided as a modern-day Gordon Gekko, and dismissed as lacking empathy and authenticity. Most seasoned Washington observers had all but declared the race over.
Yet Romney defied the critics and, as the left-wing Guardian's Jonathan Freedland conceded, gave Obama ''such a good hiding in their first TV debate, you half expected the referee to step in and end the bout on compassionate grounds''. The result is that Romney has come roaring back into contention for the presidency, with many polls now even putting him in the lead. Somewhere, Harold Wilson is feeling Obama's pain.
There are still three weeks to go before America goes to the polls, and things could change. But if the Democrats keep limping badly from Obama's wounds, many pundits are far from sure they'll heal in time. And if the Romney momentum continues, there is every reason to believe he will be the 45th president.
So it is a good time to ponder a Republican White House. What would be the defining characteristics of a president Romney? And how would a new administration deal with the world?
The most important point to bear in mind is that Romney is neither a radical nor an ideologue. Cautious, calculating, compromising — these qualities are precisely what make him suspect among those Tea Partiers who want the Republican Party to be doctrinally pure. Recall all the conservative criticisms levelled at Romney during the primary process a year ago: he was seen as either a serial flip-flopper or a closet liberal, which is heresy in Republican ranks. Such concerns were understandable, given his behaviour since 1994 when he ran as a progressive Republican against Teddy Kennedy in a Senate race in Massachusetts.
After his tenure as governor of that liberal state (2003-07), Romney decided to convert himself into a ''Reaganite'', abandoning his set of moderate positions overnight and substituting the whole conservative laundry list, virtually without qualification. From abortion and gun control to health care and emissions trading, he proved to be the political equivalent of the fictional comic-book superhero, Plastic Man.
Yet if Romney could twist himself into a conservative en route to his party's nomination, it is hardly surprising he is now turning towards the centre to win over independents who help swing elections. In the past week, he has distanced himself from evangelical Christians on abortion and allowed some wriggle room in his tax plan in order to compromise with Congress should he win office.
This lack of ideological conviction is hardly what troubles the sleep of independents. It also suggests that a president Romney would be the very soul of centre-right moderation, cautious to a fault and unlikely to take risky paths. Take foreign policy, where he relies almost entirely on a disparate and fractious team of advisers (from hardline unilateralist John Bolton to moderate realist Robert Zoellick).
Romney champions a new American Century, the term coined in the 1940s to describe US global pre-eminence. In this telling, the US will impose its will and influence across the world, increasing defence budgets, confronting China and Russia, and encouraging Israel to attack Iran.
Such a grandiose agenda, however, is fundamentally incompatible with the conservative priority of downsizing government at home. It is also at odds with the reality that the US lacks the power to micro-manage a more plural world.
In a keynote foreign policy address last week, Romney — egged on by neo-conservatives from the recent Bush era — called for a new Marshall Plan in the Middle East. To capitalise on the Arab Spring, he argued, the US should help build viable democratic states, a la Washington's generous support to western Europe after World War II.
But the circumstances have changed dramatically since the days of a Pax Americana.
As Stephen Walt, a professor of international relations at Harvard University has observed, in 1948 the Marshall Plan allocated $13 billion, or 5 per cent of total GDP, in grants to kick-start Europe's economy. By contrast, in 2012, an equivalent amount would be $700 billion. There is no way that a debt-burdened Washington could devote even a tenth of that amount.
For all his American bravado on the campaign trail, a president Romney would more likely pursue a modest foreign policy with a prudent calculation of commitments and resources.