Mark Phariss and Vic Holmes live in an airy, four-bedroom house in a well-to-do West Plano subdivision, with wood floors, white walls, and a general air of middle-American tastefulness. Among framed family and vacation photos, the most striking things on the walls are four portraits, painted by San Antonio artist Pauline Howard, of Phariss and Holmes with assorted beagles they’ve owned over the years. On a night in mid-December, there was a modestly scaled Christmas tree in the foyer and a fire in the den fireplace. The two men—who describe themselves as “boring homebodies”—sat on the couch with their three current beagles, Abby, Betsy, and Jake, dozing beside them.

They may not look like rabble-rousers, but these men are engaged in a dramatic, possibly revolutionary act: suing the State of Texas for the right to marry each other.

Phariss and Holmes, who filed suit with another same-sex couple in October and whose case will be heard this month by the U.S. District Court in San Antonio, are unlikely catalysts for social change: until recently, Phariss wasn’t entirely out of the closet, and both men were deeply hesitant about being part of the case. Holmes, who is a 43-year-old physician’s assistant in Fort Worth and former Air Force officer, feared that exposing themselves so publicly might make them targets of antigay violence. Phariss, who is 54 and an attorney, worried that the attendant publicity would alienate colleagues and clients, many of whom didn’t know about his sexuality. He even asked the legal team handling the suit if it could withhold a press release from the Dallas Morning News, since that’s the newspaper that everyone he works with reads.

“The day it was filed, I literally got physically sick,” recalled Phariss. “Leading up to that, we definitely had moments where we looked at each other and asked, ‘Have we lost our minds?’ It’s no accident that my name is the last of the plaintiffs listed.”

A decade after Lawrence v. Texas—the landmark 2003 Supreme Court decision that declared state laws forbidding homosexual activity to be unconstitutional—Texas seems to have found two more reluctant gay-equality activists. Like John Geddes Lawrence, who was closeted at the time of his 1998 arrest in Houston for consensual sex with another man in his own house, Phariss and Holmes found themselves drawn into the battle for marriage equality almost by happenstance. At every step of the way, they’ve had to keep convincing themselves this is the right thing to do. “The truth of the matter is I had some reticence about meeting with you,” Phariss told me.

Still, their case could end up bringing marriage equality to Texas, or even all fifty states. Arguing that bans on same-sex marriage are “repugnant to the United States Constitution,” the suit—which cites, among others, Governor Rick Perry and Attorney General Greg Abbott as defendants—asks the court to strike down the 2005 state constitutional amendment that defines marriage as between one man and one woman. The case will be heard by Judge Orlando Garcia, a Clinton appointee who showed little sympathy to Perry and Abbott in the 2012 redistricting battles.

Phariss and Holmes’s efforts are also part of a larger societal groundswell: just eight months after the Supreme Court’s United States v. Windsor decision, which said that the federal government must recognize same-sex marriages performed in states where they are legal, there is widespread sentiment that it’s merely a matter of time before same-sex marriage is legal across the country. Opinion has shifted rapidly on the issue, with recent polls saying that nearly 60 percent of Americans now believe gay marriage should be legal—compared with about 37 percent in 2006. In December alone, the Supreme Court of New Mexico issued a unanimous decision allowing for gay marriage there, and a federal judge in Utah struck down that state’s constitutional amendment defining marriage as between one man and one woman (though the U.S. Supreme Court quickly stayed the decision*). Right now, seventeen states and the District of Columbia allow same-sex marriage.

Texas would seem to be the last frontier in this battle. Few other states are as steeped in Marlboro Man mythology and social conservatism; in 2005, when the gay-marriage ban was placed on the ballot, 76 percent of voters supported it. Yet at the same time, there are long-standing tensions here, between the rural and urban areas and between the religious conservatives of the east and the live-and-let-live libertarians of the west. Jonathan Saenz, an attorney and the president of the nonprofit conservative advocacy group Texas Values, may be right when he argues that “this issue has been voted on and settled,” but settled doesn’t necessarily mean settled forever. Polling shows that a majority of Texans now support either marriage or civil unions for gays, and the numbers are moving in the direction of the supporters. “Texas has not been left out of the evolution that’s gone on around the country,” said Chuck Smith, the executive director of Equality Texas, an Austin-based gay-rights advocacy group.

Right now, the debate is playing out in the state on a number of different fronts. In November the Texas Supreme Court heard arguments in a case brought by two couples who married in other states and are now asking Texas to grant them a divorce. That same month, Houston mayor Annise Parker announced that the city would extend employee benefits to same-sex partners who married their spouses in other states, despite a recent opinion by Abbott that doing so is a violation of the state constitution (Abbott’s opinion has no legal weight). The Harris County Republicans promptly sued the City of Houston over the policy, though their suit is likely to be thrown out on the grounds that the plaintiffs have no vested interest in the matter.

The legal battle with the farthest-reaching implications is the one Phariss and Holmes are waging—a victory could bring marriage rights to the nearly 600,000 adult Texans who identified as gay or lesbian in the most recent census. The lawsuit originated with co-plaintiffs Nicole Dimetman and Cleopatra De Leon, who live in Austin but married in Massachusetts in 2009. In the aftermath of last summer’s Windsor decision, the women decided to sue Texas to recognize their marriage. One of their main motivations, they said, was to cement parental rights regarding their son, whom De Leon gave birth to in 2012 and whom Dimetman has since adopted. “We want to be able to tell our kids that we are married,” De Leon told me.

In August, Dimetman, an attorney who previously worked for the San Antonio office of Akin Gump Strauss Hauer & Feld (which had filed an amicus brief in the Windsor case), asked her former employers if they would be willing to represent the couple. After Akin Gump agreed to take on the case, the firm’s attorneys began reaching out to other gay couples, asking them to join as co-plaintiffs. They believed that a diverse group of plaintiffs—male and female, unmarried and already married in another state—would give the lawsuit its best chance. One of the first people lawyer Frank Stenger-Castro talked to was Phariss, whom he knew through legal circles. Phariss and Holmes eventually agreed to join the suit and went to the Bexar County Clerk’s office, where they requested and were denied a marriage license.

Why would Phariss and Holmes take on such a public role, given Phariss’s semi-closetedness and their concerns for their safety? They say that, in good conscience, they couldn’t not do it.

“There’s this phenomenon where someone is in trouble and needs an ambulance, and everybody says, ‘Call 911,’ and everybody assumes someone else is going to do it, and nobody winds up doing it,” said Holmes. “I didn’t see anybody else doing this, so I thought, ‘Okay, I’ll be the one who makes the call.’ ”

A long legal road lies ahead for the men: if Judge Garciawere to find in their favor, Perry and Abbott would likely appeal to the Fifth Circuit Court of Appeals, in New Orleans. From there, no matter what the decision, the case would go the U.S. Supreme Court, if the court decided to take it. But according to Kenneth Upton, a Dallas-based lawyer for the national gay-rights legal advocacy organization Lambda Legal, a marriage-equality case from another state, one that is farther along in the legal pipeline, is likely to make it to the nation’s highest court first. With this term’s docket pretty much full, the earliest the court would hear such a case is the 2014–2015 session. Many legal observers seem to think that, given its current ideological makeup and its recent pro-gay-equality decisions, the court will declare same-sex marriage legal nationwide. “They don’t like to get too far ahead of public opinion on big issues like this,” said Upton. “They let the public’s opinion come around, and then they come in and kind of play clean-up.”

Of course, even if Phariss and Holmes do eventually win the right to marry in their home state, it’s hard to imagine they will ever feel entirely at ease in a place where they had to fight to get the most basic recognition of their worth as human beings. But that doesn’t mean they’d think of leaving. When I asked the soft-spoken Phariss if he had ever considered moving to a state that more readily embraces gay people, he suddenly displayed a very Texas sort of stubbornness. “Absolutely not,” he said. “That’s not anything we would even entertain. It is inconceivable to us that we would have to move to enjoy our constitutional rights. That’s offensive.”

*Correction: A previous version of this article said the U.S. Supreme Court overturned the decision. In fact, SCOTUS stayed the decision. We regret the error.