Al Gore, who lost to George W. Bush in the 2000 presidential election, is becoming a key potential power broker in the increasingly bitter battle between Hillary Clinton and Barack Obama to win the Democrat nomination.

Gore emerged yesterday as a possible mediator who could negotiate a resolution if the primary campaign ends in a stalemate and has to be decided by the party convention, where divisions are likely to run deep.

The former vice-president, who was awarded the Nobel Peace Prize for his environmental campaign, is among a number of party 'elders' who plan to remain neutral in order to keep such an option open, the New York Times reported yesterday.

They are increasingly concerned that the momentum built up by Clinton and Obama's enthralling race could be squandered if neither lands a knockout blow and the nomination is decided at the convention by an elite of 796 Democratic 'super-delegates'. A perception that a backroom deal had ignored the wishes of millions of voters could be a gift to the Republicans, who have already in effect settled on John McCain as their candidate.

Nancy Pelosi, the House Speaker, and three candidates who have dropped out of the contest - former senator John Edwards and senators Chris Dodd and Joe Biden - have spoken to Gore recently. None has declared allegiance, although Gore is said to have been wooed by supporters of both Clinton and Obama.

Gore's possible role is especially intriguing because of his complicated history with the Clintons. Some of his allies accused Bill Clinton of concentrating more on his wife's run for the Senate in 2000 than on Gore's bid for the presidency. In turn, Bill Clinton felt snubbed when Gore did not call on his famed campaigning abilities in the final weeks of the battle with Bush.

Already the arguments over process have begun. Trailing for the first time after successive defeats in eight states since Super Tuesday, Hillary Clinton has renewed her call for the result of last month's Florida primary to count in the final reckoning. If she gets her way, it could yet push her back to pole position, assuming the contests in Texas, Ohio and Pennsylvania fall largely in her favour.

'Sure, she has a big hill to climb, but never count a Clinton out,' said Don Fowler, a former national chairman of the Democrats and a prominent supporter of her campaign.

The Florida lifeline would be thrown if the party's national leadership rescinded a decision that was supported by Obama and Clinton when it was made last summer. The Sunshine State decided it was too important to wait until after the Super Tuesday voting of 5 February and brought forward its primary to 29 January. As punishment for the breach of party rules, the state's 210 delegates were barred from August's convention.

Clinton won the ballot with 50 per cent of the vote to Obama's 33 per cent, and the same thing happened in Michigan, which Clinton won with 55 per cent of the vote and where Obama's name was not on the ballot, excluding another 156 delegates.

'The people of Michigan and Florida spoke in a very convincing way, that they want their voices and their votes to be heard,' Clinton said. 'The turnout in both places was record-breaking and I think that should be respected. They have a right to be heard just as much as anyone else.'

Obama, who leads by about 100 delegates and is 700 short of the winning post of 2,025 after victories last week in Maine, Maryland, Virginia and the District of Columbia, unsurprisingly takes a different view, given the advantage those delegates would restore to his rival.

'At the 11th hour, the Clinton campaign is trying to rewrite rules that were firmly established and I don't think there's a lot of appetite for that,' said David Plouffe, Obama's campaign manager.

But Obama has said he would be happy for the two states' delegates to attend the convention providing their participation did not affect the result. 'I think even my six-year-old would understand it would not be fair for Senator Clinton to be awarded delegates when there was no campaign,' Obama said.

With both camps lobbing insults and the issue becoming an increasing distraction before the next round of primaries in Hawaii, Washington and Wisconsin on Tuesday, and more significant elections in Texas, Ohio, Rhode Island and Vermont a week later, Democrat chairman Howard Dean is under pressure to find a solution acceptable to both sides.

Clinton has numerous other headaches as her challenge nears its make- or-break point. A tumultuous week saw her campaign manager, Patti Solis Doyle, replaced and David Wilhelm, the key strategist behind Bill Clinton's 1992 presidential campaign, declaring his support for Obama.

Moreover, there are signs that Clinton's support from prominent black leaders is eroding - the New York Times reported that veteran civil rights activist John Lewis had switched his allegiance to Obama. Exit polls at last week's primaries suggested that women voters are also turning away.

'It's been a bad week for her, but I wouldn't count her out yet,' said Michael McDonald, professor of government and politics at Virginia's George Mason University. 'Obama has never been a front-runner before and now he's receiving attacks not only from Clinton, but also John McCain. They're saying he has no substance, and the attacks that follow will colour in the picture for the voters.'

Fowler, meanwhile, laments that this latest controversy is taking place in Florida, scene of the disputed 2000 election when Democrats insist Bush 'stole' victory, and consequently the White House, from Gore by a margin of just 537 votes.

'There have been other controversial elections in our history going back to the 18th century and Florida has been a questionable state in a few of them,' he said. 'Maybe it's the heat down there that's getting to them and making them do crazy things.'

What they're saying

'I am a candidate of, from and for the middle class of America.'

Hillary Clinton

'Obama's going around issuing promissory notes on the future that he can't possibly redeem.'

Charles Krauthammer, Washington Post

'I do have my own personal political ambition, and that's to see my mom become my president.'

Chelsea Clinton

'Two weeks ago we were a bit of an underdog, now we're a slight underdog.'

Barack Obama