A week which began with Barack Obama icily turning his back on Hillary Clinton is ending with the two Democratic presidential candidates wreathed in smiles and apparent mutual admiration, even whispering into each other's ears.

The contrast between their appearances at Monday's State of the Union address in Washington and Thursday's TV debate in Los Angeles reflects a growing awareness of the damage caused by the intense, often personal, acrimony of recent weeks.

They are heading helter-skelter - almost neck-and-neck - into Tuesday's elections across 22 states for their party's nomination. But, in the midst of a pulsating campaign crackling with the historic potential to elect the first black or woman President, some Democrats are waking up to the prospect that neither of them will win.

The emergence of John McCain as the likely Republican nominee has cast a cloud of doubt over the assumption that after eight years of President Bush, America will choose a Democrat to succeed him in November. The most recent polls suggest that the mercurial Mr McCain, who appeals to many independent voters, would beat either Mrs Clinton or Mr Obama.

A race like a crackpot Dynasty

The contest between Barack Obama and Hillary Clinton matches any fiction

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BACKGROUND

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Democratic strategists have noted that in Florida this week Mr McCain secured strong backing from Latinos - an important component of the electorate which other Republican candidates alienate with hardline stances against illegal immigration.

Critics say that his liberal positions on such issues make him a figure of suspicion for many conservatives. But a senior Democratic party figure said yesterday: “The Republicans always fall into line behind their candidate in the end. The trouble is, we don't.”

Some party officials already fear a reprise of the 1988 election when the Republicans destroyed Michael Dukakis's presidential bid with charges that were first levelled against him by Al Gore, a rival for the Democratic nomination. In Thursday's debate in Hollywood, Mrs Clinton and Mr Obama sought to paper over the divisions between them.

“I was friends with Hillary Clinton before we started this campaign,” said Mr Obama. “I will be friends with Hillary Clinton after this campaign is over.” Mrs Clinton expressed similar sentiments, saying: “The differences between Barack and I pale in comparison to the differences that we have with the Republicans.”

On Monday night after Mr Bush's State of the Union speech, however, Mr Obama had been accused of snubbing Mrs Clinton. He was seen staring coldly at her and then turning away as she reached out to shake the hand of Edward Kennedy, who was seated next him after delivering a prize endorsement a few hours earlier.

The Clinton campaign may have succeeded in dragging Mr Obama into a political fist fight during the South Carolina primary, only to find the tactic had backfired. Faced with evidence that her poll lead was evaporating, she has sought the high moral ground.

Bill Clinton, accused of using racially-charged language against Mr Obama last week, has been reined in, with recent speeches barely mentioning his wife's rival. Mrs Clinton has even adopted some of Mr Obama's language, saying that she would focus her campaign on “lifting people up”.

Her aides, seeking to capitalise on the controversy over his snub, circulated dossiers detailing “personal negative attacks”. One told Mr Obama to “practise what he once preached”.

The animosity reflects a deeper gulf over the way to win the presidency. The Clintons are believed to resent a bid to stop their restoration to the White House by a politician with just three years' Senate experience.

Aides privately compare Mr Obama to Jimmy Carter, who was elected on a similar “revival of hope” message after Watergate and Vietnam but proved to be a weak President. There is little effort to conceal contempt for his promise of transcending the political and cultural divisions of America, which they believe would swiftly reappear even if Mr Obama survived the

“Republican attack machine” in a general election.

Mr Obama has argued that such a “politics-as-usual” view engenders only despair and disillusionment. This week he dismissed Mrs Clinton as a divisive figure from the past. His supporters point out that the vituperative nature of this campaign has reminded many voters, as well as Democrats from Mr Kennedy downwards, what they disliked about the Clintons - and their relationship with the truth.

On Thursday night disagreements were confined to policy differences as the candidates sparred gently over Iraq, health care and legal rights for immigrants. But, even as they spoke, their campaigns were still pouring out e-mails and leaflets attacking each other's record and judgment.

Indeed, the public display of affection in Hollywood may have had less to do with concerns about Democratic unity than the looming contests next week which are so finely balanced that neither dare risk another row. For the moment.

The big four

Hillary Clinton Hopes to capitalise on poll leads in a dozen states, including those around her New York Senate as well as California and Missouri. She expects to do well in Arkansas, where Bill was governor but is focusing on the west where the Latino vote holds sway and more delegates are at stake. She is pitching hard for Edwards supporters by emphasising economic insecurity

Barack Obama With the exception of Illinois, his home state, he faces an uphill struggle in the big states. Strategy is to target black districts while hoping Edward Kennedy’s backing can cut into Clinton’s lead among Latinos. Focusing on caucuses where his grassroots operation gives him the edge, Southern states with a high proportion of black people, and open primaries in which independents vote

John McCain Riding a wave of momentum which he hopes will make the nomination inevitable and see the Republican establishment — and donors — climb aboard the bandwagon. Loking for emphatic wins in big primaries including California and New York, where endorsements of Arnold Schwarzenegger and Rudy Giulinai should help. But he has not yet won the majority of votes in any contest and may need Huckabee to peel off social conservative votes from Romney

Mitt Romney Recognises that McCain is the clear front-runner but believes that as Huckabee fades a two-horse race will help him to put fear of God — and a maverick nominee — into the conservative base. Focus on smaller and mid-sized states, closed primaries and caucuses, where he has organisational advantage. Has a lot more money than McCain and could still mount a comeback

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