This is a misconception. Gallup did an extensive study on American Catholics (or those who identify as Catholic, anyway) and found that Catholics the nation's average in virtually every economic and education Category. About the only way that Catholics as a group differ from society in general is that they are more Hispanic (29% versus 13%) and less black (3% versus 11%) than the nation at large.
THIS ARTICLE has some interesting further details on the polling.
I am refering to the early Catholic families who came over here and started living in this country. Their descendants were indoctrinated by older family members into voting democrat, and to this day that is the way they still vote.- Tom