When Mr. Obama began his presidential campaign, Muslim Americans responded with enthusiasm, seeing him as a long-awaited champion of civil liberties, religious tolerance, and foreign diplomacy. But more than a year later, many say, he has not returned their embrace.

While the senator has visited churches and synagogues, he has yet to appear at a single mosque. Muslim and Arab American organizations say they have tried repeatedly to arrange meetings with Mr. Obama, but have been ignored.

Many are further uncomfortable with the forceful denials Obama has made in response to rumors that he is secretly Muslim.

Aides to Mr. Obama denied that he had kept his Muslim supporters at arm’s length. They cited statements in which he had spoken inclusively about American Islam and a radio advertisement he recorded for the recent campaign of Rep. Andre Carson, Democrat of Indiana, who this spring became the second Muslim elected to Congress.

In May, Mr. Obama also had a brief, private meeting with the leader of a mosque in Dearborn, Michigan, and this month a senior campaign aide met with Arab-American leaders in Dearborn.

But Rep. Keith Ellison (D-MN), the first Muslim elected to the U.S. Senate and an important Muslim supporter of the senator, was forced to cancel plans to campaign for Mr. Obama in North Carolina after an emissary for the senator told him the state was “too conservative.” Mr. Ellison said he blamed Mr. Obama’s aides – not the candidate himself – for his campaign’s standoffishness.

A similar illustration of the disconnect between Obama’s message of unity and the conduct of his campaign was illustrated by an incident in late June, when two Muslim women wearing head scarves were barred by campaign volunteers from appearing behind Mr. Obama at a rally in Detroit.

Mr. Obama telephoned the two Muslim women to apologize about the incident, a response for which he was thanked by the Arab American Anti-Discrimination Committee (ADC), which said: “You have made it clear [...] that such incidents of intolerance and disrespect will not be tolerated in your campaign just as they would not be tolerated in an Obama Administration.”

For one Muslim leader, Al-Hajj Talib’ Abdur-Rashid, imam of the Mosque of Islamic Brotherhood and twice president of the Muslim Alliance in North America, the incident illustrated one of the senator’s central challenges: how to maintain a broad electoral appeal without alienating any of the constituencies he needs to win in November. “All of the candidates have been nervous about visible Muslim presence, which they apparently view as a political liability in a public sphere greatly influenced by perception and fear,” he wrote in a letter to The New York Times.

Kareem Shora, national executive director of the ADC also wrote to The New York Times to say: “The Obama campaign has disappointed us, disappointed our passions, our hopes [...]. But we understand [the realities of politics], and we support the message of inclusion.”

President of the Virginia Muslim Political Action Committee, Mukit Hossain, said: “If they think that they are voting for a campaign that is trying to distance itself from them, my big fear is that Muslim voters will sit it out.”