Washington ? Nearly a decade after Sept. 11, less than a third of the country feels favorably toward Islam. Most Americans reflexively oppose an Islamic cultural center near ground zero, and the lower the Christian president’s approval ratings, the higher the percentage of people who think he’s Muslim.

Why?

Beyond the simplistic debate — are we patriots or bigots? — pollsters, historians and other experts say that the nation’s collective instincts toward Islam have been shaped over decades by a patchwork of factors. These include demographic trends, psychology, terrorism events, U.S. foreign policy, domestic politics, media coverage and the Internet.

Estimates of U.S. Muslims range between 2.5 million and 7 million, or about 1 percent to 2 percent of the population. There’s no official data on U.S. Muslims’ geographic distribution, but mosques are concentrated in metropolitan areas.

Most Americans are Christian, and most don’t have much direct exposure to Muslims. A quarter of Americans say they know “nothing at all” about Islam, the Pew Research Center found earlier this month, and of non-Muslims polled, 58 percent said they don’t know any Muslims.

It’s natural for people who don’t know Muslims to draw strong stereotypes from Sept. 11 and feel them reinforced by recent scares such as the Fort Hood, Texas, shootings and the Times Square bomb plot, said Leonie Huddy, the president of the International Society for Political Psychology and a political scientist at the State University of New York at Stony Brook.

“One of the things we know about cross-relationships of any kind is they become more positive as people have more personal contact with each other,” Huddy said.

‘The new outsider’

A Gallup survey last year found that Americans who don’t personally know any Muslims were twice as likely to acknowledge “a great deal” of anti-Muslim prejudice. Republicans and those without college educations tend to be less favorable toward Islam.

Muslims are “very much the new outsider,” said John Esposito, the founding director of Georgetown University’s Center for Muslim-Christian Understanding. “We’ve had Christian cults that have committed acts of violence; killings of abortion doctors. (Oklahoma City bomber Timothy) McVeigh. (However,) we have a gut context in which we place it. Muslims don’t fit that profile.”

So what shaped modern American impressions of Muslims?

Long before Sept. 11, other high-profile terrorist attacks inflamed the public imagination. Consider the killing of 11 Israeli athletes at the 1972 Olympics in Munich, the 1988 mid-air bombing of Pan American Flight 103 over Lockerbie, Scotland, which took 270 lives, and the rise of suicide bombers throughout the Middle East.

While most Muslims aren’t terrorists, most terrorist attacks on U.S. targets or allies over the past 40 years were committed by aggressors who were Muslim or Middle Eastern. Then came Sept. 11, 2001, and a decade of U.S. wars in Muslim lands.

“There have been so many acts of terrorism connected to radical Muslims that it’s not surprising Islam has a public relations problem,” said John Radsan, a former assistant general counsel for the CIA of Iranian descent who’s a professor at the William Mitchell College of Law in St. Paul, Minn.

“Most Americans up until the Iranian revolution did not experience Muslims,” Esposito said.

Iran’s 1979 revolution overthrew the Shah, whom Muslim revolutionaries denounced as a “U.S. puppet” installed by the CIA. There was little U.S. public understanding of the CIA’s role in the 1953 overthrow of a democratically elected Iranian leader and the resultant widespread Iranian public anger toward the U.S.

“When we saw people shouting ‘Death to America’ … we had no context to put that in,” Esposito said.

Leaders’ attitudes

U.S. political and cultural leaders also help shape public attitudes.

Public leaders’ reactions to the planned Islamic cultural center two blocks from the World Trade Center site offer the latest example.

Mayor Michael Bloomberg and President Barack Obama supported the project’s developers’ right to proceed, and Obama spoke out against religious discrimination. However, the president sent a mixed message when he said the next day that he wasn’t commenting on the wisdom of the project’s location — a neighborhood filled with bars, restaurants, a strip club and an off-track betting parlor.

The outspoken opposition of prominent Republicans — including Newt Gingrich and Sarah Palin — connects the Sept. 11 attacks to Islam. The issue could become divisive in some elections this November.