Video: watch the two speeches

Hillary Clinton’s campaign for the presidential nomination has accused Barack Obama of plagiarising a fellow Democrat’s speech when he delivered an address on Saturday night — an explosive accusation on the eve of today’s Wisconsin primary.

The allegation came as it emerged that Karl Rove, the former chief strategist for President Bush, has been involved in putting together an attack plan to counter Mr Obama, amid a growing Republican belief that he will win the Democratic nomination.

Howard Wolfson, the communications director for Mrs Clinton, referred reporters to a passage in Mr Obama’s speech in Milwaukee, comparing it to one delivered by his friend Deval Patrick, the Massacussetts Governor, in 2006. Referring to Martin Luther King, the Declaration of Independence and Franklin D. Roosevelt, Mr Obama said: “Don’t tell me words don’t matter. ‘I have a dream.’ Just words? ‘We hold these truths to be self-evident, that all men are created equal.’ Just words! ‘We have nothing to fear but fear itself.’ Just words — just speeches!”

That passage was almost identical to remarks delivered by Mr Patrick when he was running for office. The Clinton campaign circulated YouTube links to the speeches on Sunday.

Mrs Clinton has accused Mr Obama of being more style than substance, with soaring rhetoric lacking in policy proposals. Yesterday Mr Wolfson accused Mr Obama of plagiarism and said: “Mr Obama is running on the strength of his rhetoric and the strength of his promises and, as we have seen in the past couple of days, he’s breaking his promises and the rhetoric isn’t his own.”

Mr Wolfson’s reference to broken promises alluded to Mr Obama’s dispute with John McCain over whether he once pledged to accept public financing for the White House race itself. Such a move would limit the amount he could spend on the November election. The McCain camp has accused the Illinois senator of breaking a commitment not to use private fundraising to bankroll his campaign should he win the Democratic nomination.

Mr Obama admitted making a mistake in not crediting Mr Patrick. “He had suggested that we use these lines . . . I thought they were good lines,” Mr Obama said. “I’m sure I should [have given him credit], but didn’t this time.” An adviser to Mr Obama said that Mr Obama and Mr Patrick were close friends who “share thoughts on ideas and language”. Mr Patrick released a statement supporting the senator.

David Plouffe, a top Obama aide, said the Clinton campaign was "clutching at straws" over the plagiarism accusations, and trying to create "distractions".

The Republican attack document on Mr Obama, which emerged during a “winter retreat” session attended by Mr Rove in Los Angeles on Sunday, lists five main alleged weaknesses to be exploited if he ends up facing Mr McCain in the battle for the White House. A master of the art of defining an opponent negatively, Mr Rove has been advising Republicans how to attack Mrs Clinton and Mr Obama, but most Republicans believe an Obama candidacy poses more of a threat, especially as he is 25 years younger than Mr McCain and has been exciting independents and even some moderate Republicans.

About 75 members of the Republican National Committee were shown a PowerPoint presentation at the Beverly Wilshire Hotel outlining the main attacks that should be used against Mr Obama. They included his inexperience and lack of qualification to be commander-in-chief, according to the printed version of the presentation, first obtained by the political website Politico.com.

The third point stated that against Mr Obama, Republicans can be confident when it comes to “issues” — a clear reference to religious and values voters, and signalling that Mr Obama’s past drug use will inevitably be used against him.

In his first memoir, Dreams from My Father, published in 1995 before he entered politics, Mr Obama admitted that he used cocaine and marijuana in his youth. A campaign official for Mrs Clinton was fired in December for highlighting Mr Obama’s drug use, although several of her surrogates have also raised the issue.

It also emerged yesterday that Mr Obama had a meeting with his former rival John Edwards on Sunday, apparently hoping to secure his endorsement. The two men were filmed by a news network helicopter shaking hands and hugging outside the home of Mr Edwards. Mr Edwards dropped out of the race last month but has yet to endorse either of the remaining candidates. His backing is particularly sought because of his support among white and blue-collar workers, a key constituency in forthcoming contests in Ohio and Pennsylvania.

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