Six months after the Sept. 11, 2001, terrorist attacks, just 25 percent of Americans said Islam is more likely to encourage violence than other religions. That number has climbed to 42 percent, according to a new poll released Tuesday by the nonpartisan Pew Research Center.

The survey, conducted after the Boston bombings, found that opinions have not changed much as a result of those attacks. In March, 40 percent of Americans said Islam is more violent, 42 percent disagreed.

In the newly released poll, 46 percent of Americans disagree, Pew reported. And there are vast partisan gaps: 62 percent of Republicans say that Islam encourages more violence, compared with 39 percent of independents and 29 percent of Democrats. (The gap grows with partisan differences: 69 percent of self-described conservative Republicans say it does, 71 percent of professed liberal Democrats disagree.)

News of the poll recalls then-President George W. Bush’s aggressive efforts after the 9-11 attacks to convince Americans that Islam is a religion of peace and that extremists were trying to “hijack” the faith for their own purposes.

The overall survey had an error margin of plus or minus 2.9 percentage points. It rose to 5.7 percentage points for just Republicans, 5.2 percentage points for Democrats, and 5 percentage points for Independents.