Hillary Clinton and Barack Obama tried to focus the minds of voters on the faltering US economy yesterday but their message was drowned out by a poisonous new exchange between Bill Clinton and his wife’s rival — a dispute that is threatening to tear the Democratic party apart.

The increasingly toxic clash, in which Mr Clinton accused Mr Obama of putting out a political “hit job” on him, came as candidates on all sides began a desperate scramble for cash, having spent each other to a standstill.

With the Republican and Democratic candidates adapting their messages to focus on the economy, the financial health of their campaigns has become a significant factor in the battle for the White House as the 22-state “Super Tuesday” contest on February 5 draws near.

Mitt Romney, the one candidate with less reason for financial concerns — he has a personal fortune of $250 million (£130 million) — received a boost before the Republican primary in Florida on Tuesday. The chief executive of eBay resigned to devote her attention to his campaign, a move that could deliver a financial windfall from her contacts in Silicon Valley.

Meg Whitman, an old friend of Mr Romney who was once hired by him when he was a venture capitalist, is stepping down as head of the auction website having turned it into powerhouse in online shopping and having become a multimillionaire. Ms Whitman, who is already a consultant to Mr Romney’s campaign, said that the move would allow her to concentrate more on politics, and “to help my long-time friend Mitt”.

Mr Romney, who has raised more than $70 million, has spent much of that this year and is relying increasingly on the fortune that he amassed running Bain Capital. He has already loaned himself more than $17 million and is preparing to spends tens of millions more of his own funds on February 5, when half the delegates for the Republican and Democratic conventions will be elected.

Mr Romney, like all the candidates, now begins his rallies talking about the economy, with the credit crisis, home foreclosures and turmoil on Wall Street making it by the far the most dominant issue. His message that he is the candidate with the most business experience and acumen appears to be finding fertile ground in Florida, where a poll showed that 38 per cent of Republican voters are most concerned about the economy, compared with 19 per cent over Iraq. The former Governor of Massachusetts is in a statistical tie with John McCain in Florida. He is alo gaining ground on Mr McCain in California, the biggest prize on February 5. The other campaigns are under severe financial strain. Mrs Clinton and Mr Obama each raised more than $100 million last year before spending most of it on the early contests. They have been trying desperately to replenish their war chests with hastily arranged fundraising events as they buy slots in some of the most expensive advertising markets in America.

The Republicans, who have raised less than Democratic candidates this year, are facing an even bigger struggle. Mr McCain’s campaign, having almost gone bankrupt last year, has dragged itself back into the black but it has little cash in hand. He is counting on a win in Florida to attract funds from a Republican Establishment that has largely held back from funding any candidate this year. Mr McCain did receive one muscular endorsement yesterday — from the actor Sylvester Stallone, of Rambo fame.

Rudy Giuliani, who raised more money than any Republican last year, is understood to have spent almost all of it and desperately needs victory in Florida to stay in the race.

Mrs Clinton delivered a key speech on the economy before tomorrow’s Democratic primary in South Carolina but it was overshadowed by the intensifying war of words between her husband and the Obama campaign. Mr Obama is expected to win Saturday’s primary because of overwhelming support among black voters, who make up half the Democratic electorate there. Mrs Clinton is already focusing on Super Tuesday, especially California, where she leads Mr Obama by eight points.

Mr Clinton’s “hit job” allegations — it is unclear to what he referred — were made as Mr Obama released a radio advertisement claiming that

“Hillary Clinton will say anything to get elected”. Mr Clinton has become his wife’s chief attack dog against Mr Obama, a tactic that has forced the Illinois senator on the defensive.

— Dennis Kucinich, the longshot Democratic candidate, is due to announce his withdrawal from the race today. The left-wing Presidential hopeful said that he will not endorse another candidate.

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