By GARY ANDRES

Reprinted from Realclearpolitics.com

With all the focus on the Tea Party this election cycle, another strong predictor of political behavior – religion – has not received as much attention.

Historically, religious groups have played central roles in electoral contests, but their impact and alliances have shifted over time.

In the 19th century, Protestants dominated America numerically. They split their political allegiance between “liturgicals,” who backed the Democrats, and “pietists,” who supported the Whigs and their successors, the Republicans.

By the 20th century, religious affiliation diversified due to immigration flows. With this new population influx, the old configuration morphed into political alignments of Protestants on the side of the GOP versus Catholics, Jews, and Southern Protestants with the Democrats. Religious groups tended to vote somewhat monolithically, with the most observant the most likely to fall in line. This second religious alignment lasted at least through the election of John F. Kennedy in 1960.

Things began to change again after that. The tumult of the “Sixties,” the conservative reaction to that era (exemplified by the rise of the Christian Right), the realignment of the white South into the GOP, and the increasing willingness of Americans to join the ranks of the religious unaffiliated have all altered the linkages between religion and politics.

Today, we find evangelical Protestants as the core religious group supporting the Republican Party, joined by their Mormon allies, while a heterogeneous coalition of highly religious blacks and Hispanics, Jews, and an increasingly vocal group of seculars make up the Democrat camp. White Catholics and mainline Protestants are now the swing groups-with many of the former abandoning their close ties with Democrats and with numerous of the latter doing the same with the GOP. Denominational affiliation still matters, but beliefs and practices are more important, particularly for three of the largest religious groups: white evangelical and mainline Protestants and Anglo-Catholics.

How will this religious alignment impact the 2010 midterm elections? I recently helped conduct a poll for Resurgent Republic that provides some insights into these religious groups’ performance this fall.

The survey suggests that swing Catholic and Protestant voters are trending toward the Republicans, especially compared to 2006 and 2008 – a shift that could help the GOP win a number of closely contested House and Senate seats.

For example, among those who attend church more than once a week the GOP lead by 27 points on the ballot test (16 points among those who attend once a week). According to 2008 House exit polls, Republicans won “more than once a week” church attendees in 2008, but by a much narrower 6-point margin. Democrats lead on the generic ballot by 36 points among those who never attend church.

In addition, we found solid opportunities for the GOP with Catholics generally, and in particular with regular church attendees. While Republicans lost among Catholics in 2006 by 11-points and 13-points in 2008, they now hold a 7-point lead (39%-32%) among Catholics in general. Republicans also lead among Catholics who attend church once a week or more by 12 points.

Church attendance is even more important for Protestants in predicting political behavior. Protestants that attend church once a week or more support the GOP on the ballot test by about double the 12-point margin for Catholic regular attendees.

Although the survey did not ask religious belief questions, a born-again item was included, which can serve as a surrogate measure. Born again Protestants were much more inclined to support the GOP (+23-points on the ballot test) than their non-born again compatriots (+8). Not surprisingly, born again Protestants that attend church on a weekly basis or greater are even more committed to GOP congressional candidates, supporting Republicans by a 25-point margin.

With a month remaining until the election, the Resurgent Republic poll results finds that people of faith who attend church often – among Protestants who attend church regularly, but also in the swing Catholic category – may provide a substantial boost to Republican congressional candidates this November.

Editor’s Note: Gary Andres is Vice Chairman of Research for Dutko Worldwide and writes a weekly column for the Weekly Standard and the Hearst Newspapers.