Thanks, Republicans. The inability for the average conservative to distinguish between "terrorist" and "Muslim-American" - or even between "average Muslim (globally)" and "average Muslim-American" - is fueling this trend, as it is forcing Muslim Americans to adopt more liberal attitudes out of a knee-jerk reaction more than anything. Education levels also obviously play a role, but have been a relative constant for some time; Muslims were arguably majority-GOP as recently as 15 years ago despite being well-educated.
It's the same dynamic as what we've seen with Latinos: the negative stuff conservatives say about Mexicans may not apply to your average Latino (especially if they're not Mexican), but they know that the average conservative isn't very bright nor discerning in their application of these critiques; they essentially think everybody in [group] is the same and guilty of whatever lowest common denominators might exist.
This is why life-long Mexican citizens (along with Puerto Ricans and even Cubans, for that matter) have been shifting Democratic (Latinos as a whole were 45% GOP just 12 years ago), and why Hindus have been doing the same (majority GOP just 12 years ago): to your average Republican, "what's the difference?", and these groups know that.
Dubya was estimated to have won about 80% of the Arab Muslim vote and close to 70% of the total muslim vote in 2000
