Former President Donald Trump lost Pennsylvania in 2020 by just around 80,000 votes out of more than 6.9 million cast for president. This year, in the background of the state’s governor’s race — in which Attorney General Josh Shapiro is expected to best State Senator Doug Mastriano — there’s a tension playing out among an unlikely group of voters with the potential to change future elections there:

the tens of thousands of Pennsylvania Amish, Mennonites and other Christians in related sects who have traditionally refrained from voting.

It is the unusual campaign of Mr. Mastriano — a retired army colonel involved in efforts to overturn the 2020 presidential election — that has raised the possibility of an increased Amish vote in particular, starting with the white bonnets and Shenandoah beards that dotted the crowd at his primary victory party.

Mingled among ordinary political revelers in campaign regalia, these plainer people may have been some variety of Amish or members of the CMC, a denomination formerly known as the Conservative Mennonite Conference, to which Mr. Mastriano himself has been repeatedly linked.

The candidate’s own religious beliefs have proved difficult to nail down. The Mastriano campaign has a practice of ignoring almost all media requests; the CMC congregation in question did not respond to my repeated requests for comment.

But a debate about political participation — once sharply limited or entirely forbidden by strong religious convictions about violence, power and the state — increasingly involves the Amish, Mennonite and related communities, conservative and progressive alike. A permanent plunge into politicking would be a major break with longstanding belief and practice for these Christians. It could also have long-term political implications for the whole country, beginning in Pennsylvania but in nearby Ohio, too.

The umbrella term for these groups is Anabaptist. The Amish and Mennonites are the best known. Some Anabaptists are Plain or Old-Order, known for their distinctive dress and low-tech lifestyles. Others, like the congregation I joined as a young adult uncomfortable with flag-and-country evangelicalism, wear modern clothing and happily use the internet.

Linking these groups are a handful of historical-theological distinctives, especially rejection of violence and coercive power as incompatible with the Christian life. Anabaptism doesn’t require adherents to be apolitical or as separate from mainstream society as the Amish have tended to be, though Anabaptists have generally avoided military service.

Christians may not “employ the sword,” and it “is not appropriate for a Christian to serve as a magistrate,” declared the Anabaptist Schleitheim Confession of 1527. Jesus rejected political power and violence, the confession said, and so must his followers “so shall we not walk in darkness.”

Especially in the last decade, however, that tradition has begun to fray. Amish, Mennonite and other Anabaptist Christians are debating and practicing political engagement to a degree that once would have been unthinkable.

Mr. Mastriano’s possible ties to the CMC are a good case in point. An Associated Press photo of the victory party pictured the pastor of a CMC church where Mr. Mastriano’s wife, Rebbie, has reportedly held membership. People who appear to be Anabaptist appear in footage of campaign events where Mr. Mastriano has rallied alongside Mr. Trump and Representative Marjorie Taylor Greene of Georgia.

His candidacy has raised controversy among Pennsylvania Anabaptists, and the CMC, in its Statement of Practice, still officially rejects involvement in “any office, career or organization that requires us to employ the use of force, military service or retaliation to accomplish its objectives,” a traditional Anabaptist perspective.

The strangeness of these bedfellows is less about Mr. Mastriano’s specific platform than the very fact of his candidacy; his willingness, stated in a prayer to God, to “seize the power that we have given to us by the Constitution and by you”; his regular touting of his military service; his enthusiasm for the militaristic and vengeful Mr. Trump; and his skepticism of the separation of church and state. This would be unremarkable were we talking about support among ordinary evangelical voters. But for Anabaptists, it’s exactly the “walk in darkness” we once fundamentally eschewed.

And this shift is not unique to Pennsylvania; G.O.P. outreach and upticks in political engagement were reported in Amish communities in Michigan and especially Ohio over the past six years. Nor is it unique to Republicans. The biggest surprise of my seven years in a Mennonite Church USA congregation was how rapidly, how eagerly many of my coreligionists were diving into political action. There, the politics were typically pro-social-justice, anti-Trump progressivism — very far from Mr. Mastriano’s culture-war Republicanism. But the accelerating rush into politics was strikingly similar.

That politicization was limited in my local church, but in the broader denomination, political engagement seemed to be on an inexorable rise. At a denominational conference in 2018, I was startled by how political much of the content was. Our confession of faith looked to God for true justice, but in one conference session after another, justice seemed a primarily political hope, often tied, explicitly or by clear implication, to voting out Mr. Trump.

I’m not alone in observing this shift among Anabaptists left and right. American Mennonites are feeling the “seduction of political engagement,” the Anabaptist scholar John Roth has noted, lamenting that often their “political witness … basically aligns with the partisan divisions of the broader culture.” Mennonite Church USA’s denominational discussion around the 2020 election simply assumed political participation, and in 2020, Mennonite pastors across six denominations addressed rising political polarization in their churches.

Political operatives have taken notice, too, and in some cases are actively encouraging Amish and Mennonite forays deeper into political territory. As The Washington Post reported in 2019, Republican activists have identified the Amish and other theologically conservative Anabaptists as potential new party members, even founding a project called Amish PAC to recruit voters for Mr. Trump. The political action committee, which took in about $200,000 for the 2020 election and has reported raising about $31,000 for this cycle, has bought billboards and ads in local periodicals. Initially, many Amish people were resistant to the idea of voting, but “since 2016, every single year, it gets a little bit easier,” an Amish PAC official told The Post. “I think behaviors are finally changing.”

Increases in new voter registrations from the Amish-heavy Lancaster, Pa., area in 2020 suggest he’s right, even if the numbers remain modest. In 2016, researchers estimated, about 1,000 Amish people cast votes in the county out of about 15,000 eligible voters. The potential, though, is there for meaningful differences in close elections. And while it’s hard to get a firm tally of potential Anabaptist voters, they easily number in the tens of thousands in a few key states.

Data from Elizabethtown College’s Young Center for Anabaptist and Pietist Studies put the Pennsylvania Amish population north of 84,000, with 80,000 more in Ohio, and these numbers leave out more traditional but distinct Mennonite groups. It’s the theologically conservative factions — those more likely to vote Republican — seeing rapid growth: Pennsylvania’s Amish population nearly doubled in the last two decades. Still, it remains relatively rare today for the Amish to actually vote.

But the looming potential for the end of Amish and Mennonite wariness of politics, the disintegration of this tradition, looks to me like a weather vane in an ill wind. As American partisanship becomes more desperate and vicious, even Christians once adamant that our faith puts real constraints on pursuit of power are now inclined to shake off those strictures.

Yet however much I rue it, I can’t deny this is where many Anabaptists are moving. A recent issue of Lancaster Farming ran an Amish PAC ad alongside a passionate letter to the editor headlined, “We Can’t Vote.” Two issues later, the vehement rejoinder came in a new letter: “You Can Vote.”

Bonnie Kristian (@bonniekristian) is the author of “Untrustworthy: The Knowledge Crisis Breaking Our Brains, Polluting Our Politics, and Corrupting Christian Community.” She is a columnist at Christianity Today and a fellow at Defense Priorities, a foreign policy think tank.