Two Muslim women in headscarves who were stopped this week from appearing in television shots with Barack Obama have become the latest symptom of tension between the Democratic nominee’s inclusive message and a campaign seeking to build a razor-wire protective fence around him.

Mr Obama’s aides apologised swiftly to the women, who were barred by volunteers from sitting behind the podium in separate incidents at a rally in Detroit on Monday. “This is, of course, not the policy of the campaign,” his spokesman, Bill Burton, said. “It is offensive and counter to Obama’s commitment to bring Americans together.”

One of the hijab-wearing women, Hebba Aref, 25, said: “I felt like I was discriminated against by the very person who was supposed to be bringing this change, who I could really relate to.” Her friend was told that the reason for the exclusion was the “political climate” — an apparent reference to false rumours spreading across the internet that Mr Obama is a secret Muslim.

Mr Obama is leading opinion polls — nationally and in key battleground states — but advisers remember how Michael Dukakis, the Democratic nominee in 1988, had an average eight-point lead in June of that year before losing by a mile. Others cite John Kerry’s sluggish response to smears about his war record as a reason for the Democrats’ defeat in 2004.

For all Mr Obama’s achingly cool public persona, his campaign is a highly strung organisation, which spends much of its time denying media access to the candidate or promising to “push back” — aggressively — against any story deemed to be damaging.

Last week it launched Fightthesmears.com, a website dedicated to stamping out unfounded rumours that Mr Obama is a Muslim who refuses to say the oath of allegiance or has covered up his birth certificate, and a tape in which his wife allegedly rails against the sins of “whitey”.

Indeed, Mr Obama’s campaign has shown discipline, with very few leaks or gaffes during his battle with Hillary Clinton for the Democratic nomination and now John McCain for the presidency. This week it began a concerted effort to soften Michelle Obama’s sometimes angry image, with an appearance on a daytime chat show and publication of a “family album” in a women’s magazine.

But there are also signs that such activity is beginning to try the patience of a media which complains that Mr Obama is more insulated from scrutiny then even President Bush — whose White House has become notoriously averse to most journalists. The New York Times listed complaints yesterday, such as how the campaign had prevented the filming of a meeting between Mr Obama and black civic leaders, while also refusing to provide names of religious figures he met in Chicago last week.

Leading broadcasters recently sent a letter claiming that the campaign’s efforts to control its message when Mr Obama held a meeting with Mrs Clinton, had degenerated into “deceiving the press corps”. Despite his rhetoric about reaching out to the world, Mr Obama’s aides are often disdainful of requests for information from the international press. On Wednesday, the one journalist allowed to attend Mr Obama’s fundraiser at the home of Ethel Kennedy in Virginia, spent most of the night confined to the pool-house — out of sight of the revelry.

A prominent Washington supporter justified such a reaction by saying that no other presidential candidate in history had been subject to so much misinformation. This, he acknowledged, was a function not only of the mythical Republican attack machine but also of Mr Obama’s “somewhat exotic background”, which has persuaded at least one in ten Americans that he is a Muslim.

The Democratic nominee, the son of a non-practising Muslim, spent much of his childhood at a secular school in Jakarta. He has written about his struggles for a racial and religious identity. But his efforts to underline his Christian faith have backfired, with the media focusing on remarks made by his black liberationist pastor, the Reverend Jeremiah Wright.

On Wednesday, in another instance of the febrile — sometimes farcical — atmosphere that surrounds Mr Obama, a convicted fraudster, Larry Sinclair, was able to hire a room at the National Press Club in Washington to repeat utterly unsubstantiated claims about the candidate’s involvement in sex, drugs and even murder. The allegations were, however, undermined by news of Sinclair’s arrest shortly after the press conference.

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