Hillary Clinton's sensational return to contention for the Democratic presidential nomination will ensure the party’s intensely competitive battle goes on for at least another seven weeks, until the next big contest in Pennsylvania in April.

It was a big night for Mrs Clinton, a vital restorative to a campaign that had been written off in the last few weeks. Though she still trails Barack Obama, the frontrunner, in terms of delegates to the party’s nominating convention, there was a definite sense that the momentum had changed yet again in the Democratic race. Her victories should at least be enough to reassure some of her more nervous supporters that she can still win the nomination.

Mrs Clinton won the primary election in Ohio by a comfortable margin and edged out Mr Obama in a close fight in Texas. She also won the Rhode Island primary while Mr Obama’s sole victory of the night was in the smallest state - Vermont.

Mrs Clinton’s wins only slightly dented Mr Obama’s lead in delegates for the convention. In fact, with votes still being counted in separate caucuses in Texas, it was possible that she would actually lose the delegate contest there. But, despite Mr Obama’s continuing lead, it is clear that neither candidate can win enough delegates from the primary contests that remain to clinch the nomination. The ultimate decision then will be made by hundreds of “superdelegates” – senior party officials – who get special votes in the nominating process. In the last few weeks, as Mr Obama had won eleven contests in a row, growing numbers of these delegates had been plumping for the Illinois senator. But there is now a good chance that those voters will wait awhile, at least until the outcome of the next contest in Pennsylvania on April 22. With her victories on Tuesday Mrs Clinton could make a strong case that she had won all the big states to have voted so far – California, Texas, Ohio, New York and New Jersey. Her campaign will also redouble its efforts to allow delegates from Michigan and Florida, two other big states Mrs Clinton won but whose votes were disqualified because the two broke Democratic party rules.

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BACKGROUND

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Most encouraging for Mrs Clinton was that she seemed to have reconstituted her coalition of traditional Democratic voters. These voters – blue collar workers, union members, women, older voters and Hispanics had been the keys to her victories in earlier states but she seemed to have lost her edge among them during Mr Obama’s recent winning streak.

But in both Texas and Ohio, according to the exit polls, Mrs Clinton won those voters back. She enjoyed clear majorities among women, among lower-income voters and especially among the old. She also won heavily among white men. In Texas where there is a large Latino population, she took more than 60 per cent of the Hispanic vote. In Ohio she won 70 per cent of the vote of those over 65.

There was further encouragement for Mrs Clinton in some evidence from the polling that the campaign pendulum may have swung her way in the last few days. By a margin of two to one those voters who said they made up their minds in the final few days of the campaign chose Mrs Clinton.

This might suggest that her opponent’s stumbles in the last week may have turned the tide slightly against him. Mr Obama was caught telling voters this week that he strongly opposed Nafta (the North American Free Trade Agreement) while his aides were telling the Canadian government that his position was just campaign rhetoric and would not signal a real change in policy should he win the White House. Also this week, Mr Obama’s former financial backer Tony Rezko went on trial in Chicago on charges of fraud. Mrs Clinton may also have scored with one of the most talked-about political advertisements of the campaign so far, one that, by asking the question, “Who picks up the phone in the White House at 3 O’Clock in the morning?” directly questioned Mr Obama’s experience for the presidency.

The Clinton campaign hopes that these kind of stumbles might proliferate in the next few weeks and remind both ordinary voters and the party’s superdelegates that Mr Obama, for all his charisma, is just too big a risk to take in the general election in November.

While the Democratic contest got a new lease of life on Tuesday, the Republican primary came to an end when John McCain won all four states that voted and notched up a simple majority of the delegates needed to win the nomination. Mike Huckabee, his last remaining serious opponent, graciously withdrew from the race and Sen McCain will today appear with President Bush in the Rose Garden at the White House to receive the formal benediction of the incumbent for November’s election.

While the Democrats seem condemned to battle on at least until Pennsylvania, Mr McCain has some breathing space. His first job will be to mop up remaining opposition within the Republican party from diehard conservatives. That won’t be easy and he will clearly suffer to some extent in November from continuing right-wing bitterness and disillusionment with his triumph.

But the McCain camp are confident that in the end not many conservatives are seriously going to risk allowing Barack Obama or Hillary Clinton into the White House and, for that reason, Mr McCain has already begun an eight-month long campaign of pummelling his Democratic opponent – whomever that may be.

In his victory speech on Tuesday night in Dallas, he tried a new tack – attacking the Democrats on the economy, which voters in Ohio and Texas said was the biggest issue on their minds and which right now, with the country on the brink of a recession, is toxic for Republicans.

Mr McCain said the Democrats would abrogate trade treaties, raise taxes and hurt American business.

This is brave – and, it should be said, accurate – stuff. But it’s not clear how much traction he will get with this pro-free market line in a country that has rather soured on the market of late.

Much more important for Mr McCain will be his national security arguments. He repeated these too in his speech on Tuesday night, saying he had been as firm in his support for the war in Iraq as he had been critical of its conduct, and insisting that he had been right to support the surge of troops in Iraq last year and that the Democrats had been wrong to oppose it.

It’s a tricky strategy. The aim is to distance himself from President Bush on the war’s conduct, but claim authorship of the late surge – the one aspect of military strategy in the last few years that has worked. If the situation in Iraq continues to improve then he has a chance to attack Democrats for opposing the surge. The odds on his succeeding are long, but then again the odds on his winning the Republican nomination were even longer six months ago.

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