Analysis | How Super Tuesday unfolded | Clinton booed | Video: Obama speech | Video: Clinton speech | McCain leads | Pictures

Long, protracted leadership struggles are generally deemed to be damaging for a political party. The longer an election campaign goes on, the more it tears away at the scabs that barely cover the wounds on the skin of any political movement. A failure to unite around a winner usually suggests a deeper fissure and is often a portent of disaster when the party has to submit itself to the voters in a general election.

But after Super Tuesday, with about half the votes now cast in the primary elections for the 2008 presidential election, the two US political parties present a paradox.

The Democrats are locked in the tightest leadership battle in modern history. The Republicans have more or less settled on a candidate for November. But behind their divided leadership, Democrats are united as almost never before. Republicans, meanwhile, are preparing to divide behind their chosen leader.

Barack Obama and Hillary Clinton emerged from Super Tuesday in something close to a dead heat in the race for the Democratic nomination. The two candidates split the difference in the 22 states that voted. Mrs Clinton took 49 per cent to Mr Obama’s 48 per cent. Though she took the biggest prizes of the night in California and New York, he won heavily in smaller states. Since Democrats allocate delegates to their nominating convention in almost exact proportion to the share of the votes cast in each state, the two candidates are tied, with neither anywhere near the magic 2,025 needed for a majority.

It is virtually inevitable now that the contest will go on for weeks, if not months. This weekend a number of states likely to be favourable to Mr Obama will vote – Louisiana, Washington, Nebraska and Maine.

Next week, in the so-called Potomac primary, Maryland, Virginia and Washington DC will go to the polls and Mrs Clinton may have a slight edge there. And then it will be on to a sort of mini-Super Tuesday: March 4, when Texas and Ohio, two of the largest states, will vote.

It remains quite possible that the contest will not be decided until the party’s convention in Denver in late August. The idea of a convention battle evokes for Democrats some of the worst nightmares in their history – the 1968 and 1972 struggles, for example, when the party’s activists fought long and hard over the Vietnam War and the party wound up being crushed in the general election in November.

But the 2008 reality is rather different. Though there is clearly little personal affinity between Mrs Clinton and Mr Obama, the Democratic party as a whole is as united and enthused as almost never before. There are no substantive policy differences at all between Mr Obama and Mrs Clinton, only a few intramural theological debates about precise withdrawal timetables from Iraq and what universal health insurance actually means. Exit polls on Super Tuesday revealed that more than 75 per cent of voters for each candidate said that they would be quite happy if the other won the nomination. Turnout in the Democratic primaries was higher than ever before – 50 per cent greater than in the Republican contests.

There remains a chance that the messy undercurrents of race that have bubbled fiercely through this campaign might resurface and damage the party. But the party’s hunger to take back the White House is so powerful that it seems highly unlikely to permit itself the luxury of an internecine battle.

The Republicans by contrast, seven months from their convention, have more or less wrapped up the nomination. John McCain, the Arizona senator once written off for dead, won the most states on Super Tuesday and, because the Republican allocation of delegates is skewed heavily towards the vote winner in each state, he has an almost insurmountable lead over Mitt Romney, who has blown half of his personal fortune on a completely failed bid for the presidency. Mike Huckabee, the Baptist preacher and former Arkansas Governor was the surprise of Super Tuesday – winning across the South. But he has not shown that he can win anywhere outside states with sizeable numbers of evangelical Christian voters. Mr McCain, in contrast, has now won on both coasts – California, New York, New Jersey; in the Midwest – Illinois and Missouri; and in earlier contests in the South – South Carolina and Florida.

So are the Republicans ready to seize the opportunity to bury their differences behind an inevitable champion? Of course not.

The McCain hatred that animates much of the party’s right wing shows no sign of abating. Many prominent conservatives have said they will vote Democrat rather than support someone whose eclectic mix of views on social and economic issues (antiabortion, firmly in favour of measures to combat climate change, for example) they despise. Others have generously indicated that they might be prepared to bury their differences with him if he agrees to set aside everything he has ever believed – on illegal immigration, taxes, campaign finance reform, global warming – and subscribes to their prevailing conservative orthodoxy instead.

Mr McCain will try to mend some fences. He is due to speak today at the Conservative Political Action Committee to soothe the concerns of some of his critics. But they are unlikely to be appeased easily.

The Republicans are in for a long, quarrelsome coronation of a leader many of them can’t support. The Democrats are in for a long, happy and highly productive civil war.

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