This is something that needs to be stressed, as there are those conservatives who insist that New England Puritanism is "responsible" for modern secular liberalism.
Even with all the Unitarians, Transcendentalists, and so on, New England was once very devout--and very Republican.
Massachusetts used to elect the most conservative Senators and Governors in America (think Calvin Coolidge and Cabot Lodge Sr.) through the 1940s. The Irish and French Canadian Catholic Democrats outbred them, however.