Mark J. Rozell is a professor of public policy at George Mason University, author of numerous studies on the intersection of religion and U.S. politics and a contributor to The Washington Post’s local faith leader network. His latest book is “Religion and the American Presidency.”

Modern election campaigns prominently feature appeals to religiously motivated voters. Candidates and consultants understand the powerful impact of the faith factor for many voters.

Yet there has been notably much less “God talk” by the candidates in this presidential election season than there was in 2008 and especially in 2004. President Obama and former governor Mitt Romney have mostly avoided any mention of their own religious identities and, to the extent that they have engaged in religious-based discourse, it has been of a very general nature regarding their commitments to belief in God and to how faith guides their personal and public lives.

Each candidate recognizes the downsides of emphasizing his own faith tradition, as surveys show substantial-sized minorities of voters expressing discomfort with Romney’s Mormon faith or not accepting the authenticity of Obama’s identity as a Christian.

Religious identity nonetheless remains a key factor in the election. The voting patterns of religious groupings are hard to ignore. Consider the following breakdowns, first with a look at the one-party-leaning groups:

White Evangelical Protestants comprise about one-fourth of the population and have voted overwhelmingly Republican in recent election cycles – about 72 percent for John McCain (2008) and 78 percent for George W. Bush (2004). Survey data by such respected nonpartisan organizations as the Pew Forum and Public Religion Research Institute show that Romney is faring at least as well, and perhaps even better, with this group than McCain did.

Unaffiliateds, or the religious “nones,” are nearly one-fifth of the population and are as solidly pro-Democratic as evangelical Protestants are pro-Republican. Survey data currently suggest about three-fourths of this group will vote for the president.

Black Protestants — about 8 percent of the population — are overwhelmingly pro-Democratic and surveys have this group giving almost universal support for Obama’s reelection.

Small religious minorities – several percent of the population — mostly are pro-Democratic, and these would include Muslims, Jews and a number of Eastern and New Age religious identities. Mormons of course would be the exception as a solidly Republican voting religious group.

Second, other groups divide their support between the major parties to varying degrees:

Mainline Protestants are slightly less than one-fifth of the population, and this group has voted Republican in recent election cycles, but only by small margins. The key determinant for this group is religious practice, not identity. The less religiously observant of this group has split its vote nearly evenly between the major parties in the latest two presidential election cycles, whereas the regular church-attending members of this group have favored the GOP candidates with 55 percent of the vote in 2008 and 60 percent in 2004. Survey data again show similar splits are likely this year.

Catholics comprise about one-fourth of the population and commonly are known as the “swing vote” in national elections. Yet there really is no distinctive Catholic vote, as this segment time and again in recent years has voted similarly to the general population. Examining Catholic subgroups provides useful insights, as White Catholics (lean Republican) vote differently than Latino Catholics (heavily Democratic); observant Catholics (heavily Republican) vote differently than nominal Catholics (lean Democratic). A recent Public Religion Research Institute study concludes that the possible key to victory this year in the presidential race is which group of Catholics shows up in big numbers on Election Day (and early voting).

Indeed, in what looks to be such a closely contested election, the turnout of any of the above groups is potentially critical. For example, a surge in white evangelical voting in 2004 played a key role in the reelection of George W. Bush. In 2008, Obama not only won the traditional Democratic-leaning of these groups, but also mainline Protestants and Catholics, while slightly holding down his losses among white evangelicals.

What is the path to victory in 2012?

For Romney, it is a large turnout and commanding majorities among white evangelicals and observant Catholics, a strong majority of observant mainline Protestants, and holding down his losses – or at least hoping for a tepid turnout — in the other groups.

For Obama, it is to hold the same coalition of groups that he previously carried – black Protestants, less observant white mainline Protestants, less observant Catholics, unaffiliateds, and many small religious minorities – while hoping for a lowered turnout among white evangelicals and observant Catholics.