Obama entangled in row over Muslim headscarf

The two women were told by a young campaign volunteer that they could not sit behind the podium where the candidate was appearing in Detroit on Monday because of the "political climate". The Obama campaign quickly apologised to the women and Mr Obama was careful to pose beside a woman in a hijab while in Michigan – where America's largest Muslim community lives – the next day.

One of the women, Hebba Aref, a 25-year old lawyer from Bloomfield Hills near Detroit, said: "I was coming to support him, and I felt like I was discriminated against by the very person who was supposed to be bringing this change." She said she felt betrayed by her treatment and she was dismayed that Mr Obama had not apologised in person as he did when he made a personal call to a television reporter he had dismissively called "sweetie".

There was another bump on the road for Mr Obama yesterday when he abandoned an earlier promise to accept public financing for the presidential election, which would have limited spending to $80m (£40m) per candidate. Mr Obama said it was a necessary move to combat the Republicans who were "gaming the system" to get around the limits on public spending to attack him.

Political campaigns go to great lengths to arrange a backdrop of faces to appear in photographs and on television and it is always a delicate exercise in political correctness for a candidate's advance team to pick out supporters who will support the political message.