Hillary Clinton accused Barack Obama of being dishonest with voters on the eve of their potentially decisive contests in Texas and Ohio today.

Mrs Clinton, fighting to keep her candidacy alive after 11 straight losses to her rival, pounced on a leaked memo suggesting that Mr Obama had not been truthful in his campaign rhetoric on the subject of free trade, a critical issue in economically depressed Ohio.

The two candidates continued to swap accusations before today’s primaries in Texas and Ohio, where Mrs Clinton has banked all to revitalise her attempt to reach the White House. Last night she held small poll leads in Ohio, while Mr Obama was just ahead in Texas.

Defeat in both states would almost certainly end her campaign. There are also primaries today in Rhode Island and Vermont.

A race like a crackpot Dynasty

The contest between Barack Obama and Hillary Clinton matches any fiction

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BACKGROUND

• The ascent of Barack Obama, Mr Charisma

• Decay, jobs and guns fall under the spotlight

• Free trade: Clinton/Obama's mistakes

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Yet her aides say that even if Mrs Clinton loses Texas, a victory in Ohio would probably see her press on to the contest in Pennsylvania on April 22. She believes that Mr Obama has begun to face harsher scrutiny and that the longer the nomination race continues, the more traction she will gain.

Her advisers held a conference call with reporters highlighting contributions given to Mr Obama by Antoin “Tony” Rezko, a financier from Chicago, who went on trial yesterday on charges of corruption and money-laundering. She produced a television advert questioning Mr Obama’s preparedness to be commander-in-chief.

The Illinois senator continued to attack Mrs Clinton for voting for the Iraq war and failing to read the 2002 National Intelligence estimate before she backed President Bush. Mrs Clinton also faced criticism for saying in a television interview that Mr Obama was not a Muslim “as far as I know”.

In Ohio both candidates have promised publicly to renegotiate the North American Free Trade Agreement (Nafta) between the US, Canada and Mexico, and have threatened to pull out of it if it fails to include more protections for US workers. Such protectionist rhetoric is aimed at Ohio’s large blue-collar voting bloc, where Nafta is blamed for letting foreign competition destroy US manufacturing jobs.

Yesterday a memo emerged detailing a meeting between Mr Obama’s senior economic policy adviser and Canadian officials. It appeared to show the adviser, Austan Goolsbee, assuring the Canadians that Mr Obama’s protectionist rhetoric was merely political posturing. When a story emerged in the Canadian press last week saying that an Obama adviser had told the officials that his rhetoric on Nafta was overblown, the Obama campaign denied it.

The memo said: “Goolsbee candidly acknowledged the protectionist sentiment that has emerged during the primary campaign. He cautioned that this should be viewed as more about political positioning than a clear articulation of policy plans.”

At a hastily arranged press conference in Toledo, Ohio, Mrs Clinton accused the Obama campaign of doing “the old wink-wink” with the Canadian Government. “After days of denial, the Obama campaign was confronted with a memo of a meeting . . . I don’t think people should come to Ohio and tell the people of Ohio one thing and then have your campaign tell a foreign government something else behind closed doors,” she said.

Mr Goolsbee said that the memo was an inaccurate portrayal of his discussion and said that he did not use the phrase “political positioning”. Stephen Harper, Canada's conservative Prime Minister, yesterday denied that his government had tried “to interfere” in the election by leaking the document.

Officials at the British Embassy in Washington have told The Times that they are not too worried about the trade policies of either Democrat. One said: “There is a difference between what they say to get elected and what they do afterwards.”

Mrs Clinton’s campaign has received a boost from an unlikely cast of supporters including the Joker from Batman and a haunted madman from the film The Shining.

Since its release on Friday, more than 1.2 million people have viewed a film posted on the internet by Jack Nicholson, which splices together scenes from some of the Oscar-winner’s most famous films to articulate his reasons for endorsing Clinton.

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