But they have not gone unanswered. In each community, interfaith groups led by Protestant ministers, Catholic priests, rabbis and clergy members of other faiths have defended the mosques. Often, they have been slower to organize than the mosque opponents, but their numbers have usually been larger.

The mosque proposed for the site near ground zero in Lower Manhattan cleared a final hurdle last week before the city’s Landmarks Preservation Commission, and Mayor Michael R. Bloomberg hailed the decision with a forceful speech on religious liberty. While an array of religious groups supported the project, opponents included the Anti-Defamation League, an influential Jewish group, and prominent Republicans like Sarah Palin and Newt Gingrich, the former House speaker.

A smaller controversy is occurring in Temecula, about 60 miles north of San Diego, involving a typical stew of religion, politics and anti-immigrant sentiment. A Muslim community has been there for about 12 years and expanded to 150 families who have outgrown their makeshift worship space in a warehouse, said Mahmoud Harmoush, the imam, a lecturer at California State University, San Bernardino. The group wants to build a 25,000-square-foot center, with space for classrooms and a playground, on a lot it bought in 2000.

Mr. Harmoush said the Muslim families had contributed to the local food bank, sent truckloads of supplies to New Orleans after Hurricane Katrina, and participated in music nights and Thanksgiving events with the local interfaith council.

“We do all these activities and nobody notices,” he said. “Now that we have to build our center, everybody jumps to make it an issue.”

Recently, a small group of activists became alarmed about the mosque. Diana Serafin, a grandmother who lost her job in tech support this year, said she reached out to others she knew from attending Tea Party events and anti-immigration rallies. She said they read books by critics of Islam, including former Muslims like Walid Shoebat, Wafa Sultan and Manoucher Bakh. She also attended a meeting of the local chapter of ACT! for America, a Florida-based group that says its purpose is to defend Western civilization against Islam.