Barack Obama side-stepped the West Virginia primary tonight by beginning a sweep through states that have already had Democratic primaries - but are marked out as battlegrounds for the election in November.

Only hours before Mrs Clinton was due to speak in Charleston, Mr Obama was scheduled to appear at a economic forum in Macomb County, Missouri, an area dominated by working-class swing voters or so-called Reagan Democrats.

Tomorrow, when Mrs Clinton is expected to meet her big donors and advisers for a meeting about the future of her presidential bid, Mr Obama plans to campaign in the blue-collar, economically blighted state of Michigan.

The two candidates spoke together for five minutes on the floor of the US Senate, after returning to Washington to cast votes. It was an outwardly friendly encounter, with Mrs Clinton refusing to take a mobile phone call to continue the conversation.

David Axelrod, Mr Obama's chief strategist, said today that tonight's primary would change nothing, as he highlighted polls suggesting that his candidate was well placed to beat John McCain in the general election.

Mr Obama himself used a visit of only four hours to West Virginia on Monday to take the unusual step of conceding that Mrs Clinton would win the state. Before he left he visited a pool hall, where he displayed some ability at this man-of-the-people sport - in contrast to the lamentable performance at a bowling alley in Pennsylvania last month that had reinforced impressions he was a liberal elitist.

Asked by a reporter if voters in white and culturally conservative West Virginia regarded him as “un-American”, Mr Obama replied that he hoped they would realise he was a “practising Christian” whose grandfather fought in the Second World War and that “I was raised to love America”. His visit to Michigan is laced with added significance because it has already voted for Mrs Clinton.

Delegates elected from Michigan's primary in January - when Mr Obama's name was not even on the ballot - have been barred from the Democratic convention because it was held in breach of party rules. Mr Obama is keen to appease those angered by the decision to ignore the results of its Democratic primary. Next week Mr Obama is expected to visit Florida, which also voted for Mrs Clinton only to be ruled out of order by the Democratic leadership.

With an apparently insurmountable lead among delegates, the Obama campaign has recently begun to indicate for the first time that it is willing to accept a compromise by which the Michigan and Florida delegations would be seated. He received another clump of super-delegate endorsements today, taking his total to 27 in the past week. The sense of inevitability surrounding his candidacy was reinforced by the news that a right-wing website dedicated to Mrs Clinton's political demise was turning its attention to Mr Obama. The Texas-based Stophernow.com said that it was changing its name to Stophimnow.com.

One of the super-delegates to back Mr Obama today was Roy Romer, a co-chairman of Bill Clinton's 1996 re-election campaign and former Governor of Colorado. He said he was a friend of Mrs Clinton's, but added: “I believe it is not possible for Senator Clinton to get there. It is important for us super-delegates to let her know where we are so she is not misled.”

Yet Mr Obama still faces high hurdles before he can win the White House. Not only is he struggling to win support among white working-class voters, he is also encountering intense suspicion from the influential Jewish and pro-Israel lobby. Last week one of his advisers was forced to quit his campaign after The Times disclosed he had held direct talks with the militant Islamic group Hamas.

In an interview published today, Mr Obama exacerbated his difficulties by describing Israeli-Palestinian relations as a “constant sore [that] does infect all of our foreign policy”.

Eric Cantor, a Republican congressman, responded that such comments showed Mr Obama was a “politician with a deep misunderstanding of the Middle East and an innate distrust of Israel”.

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