By Dan Gilgoff, God & Country

How will the boom in Americans claiming "no religion"—25 percent of the country will fit into that category in 20 years, according to a Trinity College survey out today—alter national politics?

I see four big ways:

1. Secular voters will become an increasingly important component of the Democratic base.

In the 1990s, so-called religious nones comprised 6 percent of the Democratic Party and 6 percent of the GOP. Today, there are two and a half times as many nones—34 million Americans, or 15 percent of the country—and they account for 16 percent of Democrats, compared with just 8 percent of Republicans. Three in four of them voted for Barack Obama in the last election. Every indication is that these political trends will continue.

Even as the Democratic Party has seriously stepped up its faith outreach, then, the fact that the fastest-growing religious group in the United States is those with no religious affiliation—and that members of that group are leaning dramatically in the Democratic direction—will make the Dems pay closer attention to them.

2. American politics will become more polarized.

As more Americans leave religion, the ones left in the pews are those most committed to their faith. In a nation where church attendance is one of the best predictors of voting behavior—the more often you attend, the more likely you are to vote Republican—this polarization of religious life will spill over into the political arena, setting off more culture-war battles.

3. Republicans will have to choose between becoming a more overtly religious party and reaching out more seriously to the growing secular middle.

Secular voters once constituted an important part of the GOP coalition, but fewer than 10 percent of religious nones under age 30 are Republican. "Republican nones are getting older and continue to show an affinity to the GOP," says Juhen Navarro-Rivera, a Trinity College research fellow who helped compile the new report. "But they're not making new Republican nones."

Navarro-Rivera is still running the numbers, but his hunch is that the new generation of religious nones has been scared away from the Republican Party because of its ties to the Christian right. Does the GOP continue to embrace that movement or move more to the middle? Call it the Sarah Palin option versus the John McCain option. (Though opposition to healthcare reform, it should be noted, is helping bring the two camps together.)

4. If secular voters become more aggressively antireligious, the Democrats' newfound faithiness faces big challenges.

If religious nones congeal into a coherent voting bloc with their own issues, Democrats will have to pay more attention to their political agenda. Most religious nones aren't hostile to religion; few are atheists. "They're aligning with the Democrats because the party has lots of religious people, but they're not pushy about it," says Navarro-Rivera.

At the same time, religious nones aren't crazy about a huge role for religion in government and politics. And as their numbers grow, some expect them to turn more overtly antireligious. Will they continue to tolerate a party leader who invites Rick Warren to his inauguration and who refuses to decide whether religious groups can hire based on religion with government funds? Doubtful.

See President Obama's top faith moments.