Much ink has been spilled and plenty of research done about white evangelical, Catholic and Jewish voters' swing potential this year. Now, a closer look at last month's study from Calvin College's Henry Institute turns up another religious demographic that's breaking away from their traditional voting habits -- mainline protestants (a group historically tilted toward the GOP).

According to the study, 46 percent identify as Democrats and 37 percent say they're Republicans. It's the first time more mainliners have identified with the Democratic party since the New Deal (that's a big deal).

And this has not been a knee-jerk, election year reaction to Obama's use of some Jesus words. A recent Christian Century piece identifies mainliners' steady "slippage" from the Republican ranks. John Dart notes that through 2000, half of mainline Protestants saw a Republican in the mirror but by 2004, the GOP's advantage had slimmed down to 44-38.

For an explanation, Dart looks to Calvin's Corwin Smidt, who says "Social justice issues and the Iraq war might have been the major influences for change by centrist mainline Protestants."

Dart notes some historical context, as well:

Mainline churches were known for having activist leaders who called for change in the social revolutions of the 1960s and 1970s, and in later years brought more women into leadership and struggled with gay issues. "The leadership and clergy acted as the vanguard in the prophetic mode," said Smidt, "and maybe over the years this might have had some impact."

For years, members of the Religious Right have used wedge issues in an attempt to paint protestants into a conservative corner. Looks like the strategy is wearing off.