Dejected Hillary sheds a tear as Obama surges ahead

When Penn Rhodeen, Ms Clinton's mentor at Yale and an old friend, who was introducing her, referred to "our magnificent Hillary", Ms Clinton wiped away a tear and looked visibly moved.

Onlookers were reminded of her emotional appearance before the key votes in New Hampshire.

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Hillary Clinton looks emotional on the eve of tomorrow's crucial Super Tuesday contest

Yet Barack Obama has overtaken Ms Clinton in polls in the key state of California while the former first lady's support also appeared to be dwindling in other states she had counted on winning in tomorrow's Super Tuesday primaries.

Mr Obama, 46, insisted last night, however, that he was still the underdog in the Democratic race.

All the candidates are shuttling around the U.S. in a last round of campaigning before tomorrow's vote - the biggest in a series to select each party's presidential candidates.

Mrs Clinton, 60, and 71-year- old Republican John McCain remain the national favourites to boost their chances of fighting the November 4 presidential election.

If opinion polls are to be believed, former Vietnam PoW Mr McCain's overwhelming 20-point lead over his closest rival Mitt Romney should be sufficient to give him an unassailable lead once the smoke clears on Wednesday morning.

The Arizona senator appeared to have no doubts yesterday, telling supporters: "I assume I will get our party's nomination."

The 24 states going to the polls tomorrow account for half of the delegates to the partys' national conventions in August and September-where the triumphant nominees will be crowned.

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The latest Washington Post/ABC poll put Mrs Clinton on 47 per cent nationally to Mr Obama's 43 per cent.

Democrat analysts suggested the contest may remain too close to call even after tomorrow's votes are counted.

In California, where 370 delegates are up for grabs, Mr Obama was leading by 45 per cent to 41 per cent in one poll. Another gave him a 1 per cent lead.

Until a couple of days ago, Mrs Clinton was expecting to win the state by a comfortable margin.

Illinois senator Mr Obama deployed his showbusiness supporter Oprah Winfrey in California yesterday while former president Bill Clinton was putting the case for his wife.

Mrs Clinton, her voice worn ragged by countless stump speeches, tracked from California across New Mexico and Arizona.

With victories in New Hampshire and Nevada already under her belt, she was trying to shore up her power base in delegate-heavy states such as California, New York and New Jersey.

Trying to whip up support in the smaller heartland states, Mr Obama swept through Idaho, where only 18 delegate votes are up for grabs, then on to Minnesota and Missouri. Apart from one blip in 1956, Missouri has always voted for the candidate who eventually captures the Oval Office.

In spite of the fervour over his attempt to become the first black president, Mr Obama was determined to play down his prospects, saying: 'I don't think there's any doubt that Senator Clinton is still the favourite.

"When folks know me and my record, we do well. If they don't, she's got the advantages."

Mr McCain took the opposite tack as he barnstormed through the southern states.

"From what we see in the polls, there is a very good chance it could be over on Tuesday," he declared. "The sooner we get that done, the sooner I can go to work uniting the party."

His only realistic rival, Mr Romney, 60, took heart from a victory on Saturday in Maine, where he captured more than 50 per cent of the vote. Mike Huckabee, 53, is hoping to resurrect his fading hopes with a high turnout of conservative Christian evangelicals in the Deep South.