(RNS) — In a shift that stands to impact both religion and politics, survey data suggests that the percentage of Americans who don’t affiliate with any specific religious tradition is now roughly the same as those who identify as evangelical or Catholic.

According to newly released General Social Survey data analyzed by Ryan P. Burge of Eastern Illinois University, Americans claiming "no religion” — sometimes referred to as “nones” because of how they answer the question “what is your religious tradition?” — now represent about 23.1 percent of the population, up from 21.6 percent in 2016. People claiming evangelicalism, by contrast, now represent 22.5 percent of Americans, a slight dip from 23.9 percent in 2016.

That makes the two groups statistically tied with Catholics (23 percent) as the largest religious — or nonreligious — groupings in the country.

“Nones have been on the march for a long time now," Burge said. "It’s been a constant, steady increase for 20 years now. If the trend line kept up, we knew this was going to happen.”

The 2018 GSS was just released and there's some big news. Those of "no religion" (23.1%) are statistically the same size as evangelicals (22.8%). There was also a small resurgence of mainline Protestants, while Catholics are down 3% in the last four years. pic.twitter.com/uiyDSe7M6f — Ryan Burge 📊 (@ryanburge) March 20, 2019

The shift could signify coming political changes. Evangelicals often lean conservative and are known to have outsized influence on American elections: According to exit polls, white evangelicals alone made up 26 percent of the electorate in 2016, even as their share of the American population has dipped far below that, according to Public Religion Research Institute.

"Evangelicals punch way above their weight," Burge said. "They turn out a bunch at the ballot box. That’s largely a function of the fact that they’re white and they're old."

A rising tide of religiously unaffiliated voters — a group that a 2016 PRRI analysis found skews young and liberal — could potentially offset that influence. But the same PRRI analysis also noted that religiously unaffiliated Americans do not vote in the same percentages as evangelicals, and are often underrepresented at the polls.

As such, the most immediate impact of the rise in religiously unaffiliated is likely to be felt in religious communities themselves, where their absence will be noted. Even then, those who claim “no religion” are not inherently atheists or agnostics: A 2017 Pew Research survey found that only 22 percent of “nones” listed not believing in God as the most important reason for their lack of religious affiliation.

But while most religious groups in the GSS survey either saw dips in affiliation or remained roughly consistent — such as black Protestants and those listed as "other faiths" — one group did see an increase: Mainline Protestants, who have been declining at a steady clip for decades, saw their numbers tick up slightly, from 10.2 percent to 10.8 percent.

Even so, Burge noted that the change is not statistically significant, and more years would have to pass to register if it signifies a resurgence among mainliners. In the meantime, he pointed to another trend: The rise of the religiously unaffiliated tracks closely with the decline of mainline Protestantism beginning in the early 1990s.

"The biggest story is that 'no religion' is coming from the mainline," he said. "Mainliners are jumping ship."