Appeals to religious voters are a staple of modern presidential campaigns. Yet “God talk” by the major party nominees has been largely quiet in this presidential campaign season, especially when compared to election cycles in the 1990s and 2000s.

Religious identity nonetheless remains a key factor in the election. Hillary Clinton and Donald J. Trump cannot ignore the very distinctive voting patterns of religious groupings in modern presidential elections.

First, consider the following voting breakdowns in the voting populations among the one-party-leaning groups:

White Evangelical Protestants comprise about one-fifth of the U.S. population and have voted overwhelmingly Republican in recent election cycles: 79 percent for Mitt Romney (2012), 72 percent for John McCain (2008), 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 Mr. Trump is holding very strong support with this group.

Unaffiliateds, or the religious “nones,” are also nearly one-fifth of the population and are almost as solidly pro-Democratic as Evangelical Protestants are pro-Republican. They comprise firm support for Ms. Clinton.

Black Protestants — just under 10 percent of the population — are overwhelmingly pro-Democratic, and surveys have this group giving almost universal support for Ms. Clinton.Small religious minorities — several percent of the population — mostly are pro-Democratic; these would include Muslims, Jews and a number of Eastern and New Age religious identities. Mormons are an exception among religious minorities 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 relatively 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 three presidential election cycles, whereas the regular church-attending members of this group have favored the GOP nominees. Survey data 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, however, as white Catholics lean Republican, while Latino Catholics are heavily Democratic; and observant Catholics are heavily Republican, whereas nominal Catholics lean Democratic. A possible key to victory this year in the presidential race is which group of Catholics shows up in big numbers on Election Day and for early voting.

Indeed, in 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 re-election of George W. Bush. In 2008 and 2012, Barack Obama won the traditional Democratic-leaning religions and unaffiliated voters as well as the Catholic swing vote. In the George W. Bush and Barack Obama elections, significant upswings in turnout among core supporters were key to victory.

What is the path to victory in 2016?

For Mr. Trump, 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 Ms. Clinton, it is to hold the same coalition of groups that Mr. Obama 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.

Ms. Clinton and Mr. Trump themselves may not say much directly about religion in this election, but their campaigns surely will be working hard to court key religious blocs, as all recognize the powerfully important role that faith plays in presidential elections.

Mark J. Rozell is dean of the Schar School of Policy and Government at George Mason University. Among his latest books is “Religion and the American Presidency” (Palgrave MacMillan Press). Twitter: MarkJRozellGMU.