For the candidates, it could be the weekend before the presidential election itself: an endless blur of states and airports and rallies, thousands of miles apart but all looking the same, of campaign days starting and ending at dawn.
Hillary Clinton and Barack Obama, John McCain, Mitt Romney and Mike Huckabee must be shattered. But somehow they keep going, fuelled by the adrenaline of the chase and – in other circumstances – the knowledge that, win or lose, the whole thing will be over in 72 hours. Not this time, though. Welcome to America's national primary, which may settle nothing.
Every presidential year has its "Super Tuesday", a cluster of primaries that often determines the Democratic and Republican nominees for the final duel in November. But nothing has ever come close to Super Tuesday 2008. The day after tomorrow, 24 states, including such giants as California, New York, Illinois and New Jersey, will hold primaries or caucuses. At stake for both parties will be roughly the number of delegates needed to win the nomination at the two conventions late this summer.
Until recently, 5 February was shaping up as the finish line of a frantic sprint that began with the Iowa caucuses, held exactly a month ago today – a month that feels like an eternity. But although the field on each side has been whittled down to two, these political semi-finals could be more protracted. The odds must be that Mr McCain will take decisive command of the Republican race – but barring a sensation, even Super Tuesday will not resolve the fluctuating, utterly enthralling battle between Senator Clinton and Senator Obama for the Democratic crown.
And if the geographical sweep of this week's battle is without precedent, so is the interest of the public. The contests to date in Iowa, New Hampshire, Nevada, South Carolina and Florida have drawn record turnouts of Democrats, while an astonishing 8.3 million watched the Obama-Clinton debate on Thursday, a TV audience unsurpassed for a primary-season clash.
Super Tuesday falls just two days after the Super Bowl, the biggest event in the American sporting calendar. In a normal political year, the game on the football field would eclipse the contest in the voting booths. Not in 2008, however. An ABC News survey found that 40 per cent of Americans were more excited about Super Bowl XLII, and 37 per cent about Super Tuesday – a statistical tie, as the pollsters say, "within the margin of error".
Nonetheless, on the Republican side at least, some clarity is emerging. After his miserable third place in Florida, the withdrawal of Rudy Giuliani, former mayor of New York, has in practice narrowed the race to a contest between Mr McCain and Mr Romney. Mike Huckabee, the conservative ex-governor of Arkansas, is still a candidate. But with limited appeal and even more limited money at his disposal, he has no chance of victory. In the meantime the tide is running strongly in Senator McCain's direction.
After his back-to-back wins in South Carolina and Florida, the Arizona senator has what the first President Bush famously called "the Big Mo" – the momentum that generates money, big-name endorsements and, most important, a growing sense of inevitability. Last summer, as his campaign coffers emptied, top staffers abandoned him, his unpopular stands on Iraq and immigration saw him slip to single digits in the polls, he looked doomed. We may be about to witness a comeback for the ages.
With Mr Giuliani gone, he has lost his main rival for the moderate Republican vote. Mr Huckabee, meanwhile, seems to work in tacit collusion with Senator McCain (with his eye on the vice-presidential slot, many say), often defending the Arizona senator from attacks by Mr Romney, while continuing to syphon conservative votes from Mr McCain's principal rival. Better still, last week's endorsement by the former mayor can only strengthen Senator McCain in the delegate-rich north-eastern states of New York and New Jersey, where the former New York mayor is still popular.
Similarly, Thursday's endorsement by Governor Arnold Schwarzenegger can only help in California, the biggest prize on Tuesday, with 170 Republican delegates, roughly a sixth of the total needed for the nomination at the convention in Minneapolis at the start of September.
Perhaps most important, the Republican establishment which long distrusted Mr McCain is now starting to close ranks behind someone who looks a winner – who, according to the polls, has the best chance of defeating any Democrat in November. One straw in the wind was the blessing conferred on him on Friday by Theodore Olson, a former solicitor general and a leading conservative lawyer. As a result, funds are at last flowing in – a colossal relief for a man who last November had to take out a special life insurance policy to secure a $3m bank credit that allowed him to stay in the race.
Mr Romney, vastly wealthy, photogenic and articulate, yet still unconvincing to many Americans, is banking on the Midwestern and southern states, plus Mormon Utah and his adopted home state of Massachusetts, which hold primaries on Tuesday, to keep him afloat. But the winner-takes-all system used in many Republican primaries militates against him. Senator McCain is ahead in the biggest states, as well as his native Arizona. By Tuesday night he may have amassed enough delegates to be unstoppable, even if he remains short of an outright majority.
No such outcome is likely on the Democratic side. At first glance the terrain clearly favours Mrs Clinton. Three key states voting that day – New Jersey, Connecticut and New York, which she represents in the Senate – are home turf, or close to it. So too is Arkansas, where she lived before her husband became President.
Although Senator Obama is closing the gap in California (see story below), Mrs Clinton still leads in a state that alone accounts for 370 pledged delegates, 22 per cent of the total at stake this week and a sixth of the 2,025 needed to be sure of the nomination when Democrats hold their convention in Denver in late August.
Beyond doubt Mr Obama is eating into Mrs Clinton's once commanding national lead, now down to just 4 per cent in one tracking poll. But the Clinton brand should never be underestimated. The most telling result of the past 10 days may not have been Mr Obama's galvanising victory in South Carolina, but her equally clear-cut win in the Democratic "non-primary" in Florida last Tuesday.
It didn't count: no delegates were awarded, no candidate campaigned there and precious little was written about it. Yet Florida Democrats turned out in droves to give her 50 per cent of their votes, against 33 per cent for Mr Obama and 14 per cent to John Edwards, who dropped out of the race the next day.
The result mattered hugely, for two reasons. Senator Obama, with his inspiring oratory and personal charisma, may be unbeatable in small live settings. But Florida showed Mrs Clinton with a clear edge in an urban state, demonstrating her strength among Hispanic voters. Second, it is virtually inconceivable that Florida would be barred from having a say at the convention, were the nomination still to be open. What Democrat in his right mind would alienate party activists in a state which – as 2000 so painfully proved – is crucial in presidential elections? Once again, advantage Clinton.
Nonetheless, Senator Obama is on a roll. Thursday's debate was probably a draw, but it came in a week of important endorsements – including those of the Democratic patriarch Ted Kennedy, of MoveOn.org, the influential grassroots organisation with an email list of 1.7 million, and yesterday of the Los Angeles Times, California's most important newspaper. How much difference endorsements make is arguable, but candidates vie for them fiercely.
And even if he loses California, New York and New Jersey, he will still win a rich haul, under party rules that award delegates on a proportional basis – meaning that narrow defeat is worth almost as much as narrow victory. Mr Obama, moreover, can legitimately expect more than a few wins of his own on Tuesday: in his home state, Illinois, perhaps in neighbouring Missouri, the eternal bellwether of US presidential politics, in the southern states of Alabama and Georgia, and in Colorado and New Mexico, which hold not primaries but caucuses, a format that usually benefits him.
Last but not least, he has money. Mrs Clinton is anything but short of cash, but in January Mr Obama raised $32m, the most by any candidate in a single month in this election cycle. As a result, he has been running TV ads in 20 of the 22 states with Democrat polls, compared with 12 for Mrs Clinton. Now that the campaign has moved from retail politics to wholesale, such a strategy could have a vital impact.But no one really knows. The imponderables are too numerous. What will happen to the Edwards vote? Will race be a determining factor? Will either candidate make a major blunder? Most basic of all, will Mrs Clinton's "experience" argument trump Americans' desire for the change embodied by Mr Obama?
Super Tuesday may provide some of the answers, but not all of them.
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