(The Conversation) — After climbing for decades, the percentage of Americans with no religion has leveled off. For the past few years, the share of adults who identify as atheist, agnostic or “nothing in particular” has stood at about 29%, according to a major study the Pew Research Center released Feb. 26, 2025.

But this hardly means that the “nones,” or their impact on American life, are going away. In fact, their sheer size makes it likely that they will increase in political prominence.

It will presumably come as no surprise that many secular voters lean to the political left. It may, however, be surprising to learn that a fairly large number of nonreligious voters supported President Donald Trump in the 2020 and 2024 elections.

If the above paragraph is a head-scratcher, that is because “nonreligious” and “secular” are often treated as two ways of saying the same thing. But as political scientists who study religion – and the lack thereof – we have found that there is a fundamental difference between the two. While conventional wisdom holds that religious voters are Republicans and nonreligious voters are Democrats, the reality is more complicated.

Nonreligious vs. secular

So, what is the difference between people who are nonreligious vs. those who are secular?

The nonreligious tend to define themselves by what they are not: for example, not belonging to a religion, not attending worship services, not believing in God. In our surveys, many people without a religious affiliation do not cite any particular worldview or philosophy when asked what guides their life.

Secular people, on the other hand, define themselves by what they are: someone who has embraced a humanistic and even scientific worldview. That is, when asked about where they find truth, they turn to sources such as science and philosophy instead of scripture and religious teachings. Often, they identify as atheist, agnostic or humanist.

There are secular people, however, who also embrace some aspects of faith. Religiosity and secularity are not in a zero-sum relationship: more of one does not necessarily mean less of the other. In our research, we found many cases of people who belong to a religious congregation yet have a secular worldview: This describes many Jews, mainline Protestants and even Catholics, for example.

4 groups

To get a better sense of Americans’ views, for over a decade we have worked on developing questions to identify people with a secular outlook, while also asking about religious commitment, such as how often someone attends services. Our findings culminated in the 2021 book “Secular Surge: A New Fault Line in American Politics.”

Based on the results, we can divide the U.S. population into four groups: Religionists, Nonreligionists, Secularists and Religious Secularists.

The Religionists category includes people of all faiths. At 41%, this is the largest group in the United States, but they do not form a majority.

Secularists make up 27% of the population – larger than the percentage of any single religious tradition. Evangelical Christians, for example, are 23% of the U.S. population, according to Pew, and Catholics are 19%.

Another 14% of Americans are what we call Religious Secularists: people who identify with and participate in a religious community, yet have a secular worldview. They might attend worship services but consider their religion more as an expression of their culture than a source of teachings to inform their daily decision-making. Some Religious Secularists may describe themselves as agnostic or even atheist.

Finally, 18% of Americans are Nonreligionists: These are people we described above as not having any religion in their lives, but neither do they have a secular worldview. They are defined by what they are not, not what they are.

Political views

These four groups vary in whether they are politically engaged – and if so, whom they support.

In our book about America’s “secular surge” we used data from a nationwide survey in 2017. In 2021, we conducted a second wave of that survey.

According to data from that survey that we analyzed for this article, Religionists and Secularists are about equally likely to get involved in politics: roughly 30% of both groups reported doing something political in the past 12 months, such as attending a rally, volunteering for a candidate or donating money. Nonreligionists were much less likely: only 17%.

In fact, no matter the form of civic engagement – voting, volunteering – Nonreligionists were consistently the least likely to be involved. Only 30% of Nonreligionists report belonging to any sort of club or organization, while for the rest of the population, it is closer to 50%.

In the same 2021 survey, we asked people to rate various politicians on a 0-100 scale, with a higher number meaning a more positive view.

On average, Religionists rated Trump a 61, the highest of the four groups; Secularists give him the lowest score, at 14. Nonreligionists gave Trump 47 points.

It would be wrong, however, to call the Nonreligionists an ideologically conservative group.

Consider their ratings of Bernie Sanders, who caucuses with the Democratic Party but describes himself as a democratic socialist. For three of the groups, support for Sanders was the mirror opposite of their feelings toward Trump, a Republican. Secularists, for instance, gave the Vermont senator a relatively high score of 66, on average; Religionists’ feelings toward him are much cooler, at 32 points.

By contrast, Nonreligionists gave a nearly identical rating to Trump and Sanders. Given that the two men are at opposite ideological poles, how could Nonreligionists rate them the same? We suspect it is because both figures challenge the status quo.

In 2024, the Trump campaign worked to mobilize “low-propensity voters”: political jargon for people with the low levels of civic engagement often found among Nonreligionists. Not only are they politically disengaged, they are the most likely to combine being young, male, white and without a college degree.

A ‘secular left’?

Secularists, too, are disproportionately young and white. But in other ways they are very different from Nonreligionists. Secularists typically have a college degree and are evenly balanced between women and men. Typically, they are also liberal and highly engaged in politics.

So how will they shape American politics? The answer may depend on whether Secularists cohere into a movement – a secular left to parallel the religious right.

Today, highly religious conservatives are a vocal group within American politics, the core of the Republican Party. A generation ago, however, they were a disparate group of people from different Christian denominations, from Baptists to Pentecostals. Many of the religious groups that now march in common cause once had sharp disagreements.

It remains to be seen whether secular voters will organize in a similar way. Either way, it is safe to say America’s religious composition has changed significantly.

Don’t assume, however, that a turn away from religion necessarily means a sharp turn toward the political left. We’d caution that the story is more complicated. For now, secular voters lean to the left – but nonreligious voters are up for grabs.

Geoffrey C. Layman and David E. Campbell received funding from the National Science Foundation.

(David Campbell, Packey J. Dee Professor of American Democracy, University of Notre Dame. Geoffrey C. Layman, Professor of Political Science, University of Notre Dame. The views expressed in this commentary do not necessarily reflect those of Religion News Service.)