The movement for gay marriage is one of the most successful issue campaigns of the last several decades, having convinced the American public—and the Supreme Court—that an issue once considered ridiculous was a matter of basic rights.

So it’s no wonder that a lot of causes, particularly on the left, now want to copy the effort.

“What I’m finding is that there is a real hunger to put one foot ahead of the other on progressive causes,” says Marc Solomon, the national campaign director for Freedom to Marry, one of the leading groups pushing for gay marriage. (Now that the Supreme Court has made gay marriage legal across the country, the organization is winding down and will disband later this year.)

The marriage campaign’s major innovation was fusing litigation with a political campaign, using lawsuits and state-level political victories to reinforce one another. The combination worked to create an impression of momentum even as the tide of public opinion gradually turned. “What’s really compelling to people is this idea of a campaign that drives a national narrative, but the work is largely in the states,” Solomon told me recently.

Solomon is in demand as a speaker these days. When I talked to him last week, over lunch in New York’s Chelsea neighborhood, he was getting ready to go to California and give a presentation to a group of criminal-justice reformers. He’s already worked extensively with gun-control advocates, and he’s fielded requests from climate-change activists, poverty fighters, women’s-rights groups, and immigration reformers, to name a few. (Some conservative activists—including the very social conservatives who opposed the spread of gay marriage—are also looking to the marriage campaign for inspiration.)

Solomon wrote the book on winning marriage: It’s called Winning Marriage, and it’s a great read for political junkies, giving the full blow-by-blow of the underdog effort. Released last year, the book is getting a Supreme Court epilogue for its paperback edition this fall.

The quest for gay marriage had some unique features. Most other issue campaigns, for example, have Congress as their ultimate target, not the courts (though the environmental movement has long used lawsuits to advance its aims, including the elimination of coal plants). But the basic design—strategically targeting states to create momentum for national change—could still apply.

The first lesson other campaigns could learn from the marriage movement, Solomon told me, is: Use state and local politics to put points on the board. With Washington so gridlocked that virtually nothing gets done, the hopes of many reform groups—immigration, climate, gun control, the minimum wage—have run aground even when there appeared to be enough votes in Congress to pass a measure. But municipalities and states have become laboratories for reform, as they were with marriage. Gun-control campaigners won a referendum in Washington state last year, and numerous states and cities have recently hiked their minimum wages.

The key, Solomon says, is to ruthlessly pick the right targets based on careful research and a tough-minded willingness to say “no” to well-intentioned local leaders; losses can set a movement back. It’s also important, he says, to go on offense when possible. For a decade, gay marriage was a consistent loser in ballot measures sought by social conservatives to ban it at the state level; this kept advocates constantly on the defensive and gave opponents a powerful talking point. In 2012, Freedom to Marry carefully vetted state-level campaigns and decided to back ballot fights in Maine, Minnesota, and Washington, while lending less support to one in Maryland. When the gay-marriage side won in all four cases, it changed the issue’s political calculus nationally.

A major factor in those four state wins was an overhaul in the message used to win over voters—from an argument about the rights and benefits of marriage to one about the fundamental human desire for love and commitment. This is another lesson Solomon believes other movements could learn: Make an emotional argument based on positive values. For years, pollsters told gay-marriage advocates that attacking discrimination and invoking the Constitution were their most resonant arguments—but over and over, these cerebral ideas proved no match for the visceral appeal of the opposition’s messages about family and faith. And the emphasis on rights convinced many voters that what gay people wanted out of marriage was fundamentally different than what they thought marriage was about. It was by framing the issue in personal terms that campaigners started to win hearts and minds. This is something immigration reformers have recently tried to do by making young strivers—the “dreamers”—the human face of their movement.

The marriage campaigners spread their message using a sophisticated persuasion campaign—a tactical innovation that many others are now trying to emulate. Armies of canvassers—both paid workers and volunteers—set out to have in-depth conversations with thousands of voters using ideas developed with help from the liberal Analyst Institute, a quasi-academic campaign-tactic lab. Rather than parroting a script, the canvassers used a few open-ended prompts (“What does marriage mean to you?”) and drew on their own experiences to have long conversations about family and faith that often turned personal—and changed people’s minds.

These techniques came in for some scrutiny recently with the controversy over a study by the political scientists Michael LaCour and Donald Green that turned out to be based on fake data. The study purported to show a huge, lasting effect on people’s opinions about gay marriage when they had a personal conversation with a gay canvasser—but not a straight one. Published in Science, the study was retracted when the data forgery came to light. Had it been real, the study would have provided the first academic proof of the kind of techniques the gay-marriage campaigners pioneered. But Solomon and other advocates say they have plenty of rigorously field-tested evidence from their work that these techniques do work. (There’s no evidence, however, that a canvasser has to be gay to have an effect.) And other campaigners, notably abortion-rights advocates, are already putting similar tactics to work.

To be sure, there are some unique features of the gay-rights fight that other causes don’t share. “An advantage we have is that we are in every family,” Solomon said. “Dick Cheney never has to deal with a poor person, but he has a lesbian daughter. That makes a big difference.” Gay rights also didn’t pose a threat to anyone’s economic interests, unlike many lefty priorities—but, Solomon points out, the marriage campaigners were up against well-financed opponents on the religious right, including evangelicals and the leadership of the Catholic and Mormon churches.

Solomon, a former Republican congressional staffer from the Midwest, got his start fighting for gay rights in Massachusetts. In 2003, the state supreme court ruled that gays should be allowed to marry, and a bipartisan group of state lawmakers—from Republican Governor Mitt Romney to many Italian-American Catholic Democrats—were determined to stop it from happening by amending the state constitution. That was what happened in Hawaii in the 1990s, after a court similarly ruled in favor of gay marriage: Legislators put a constitutional amendment on the ballot to ban gay marriage, and voters overwhelmingly approved it.

Solomon’s employer at the time, MassEquality, faced a seemingly impossible task: To prevent the issue from going to the ballot, they had to get 75 percent of the state legislature on their side. In order to put grassroots pressure on lawmakers, the gay-rights campaigners got creative: They combed through state records to find the hundreds of gay couples who had already gotten married, then sent each one a postcard asking if they’d be willing to talk to their legislator. This tactic paid off in a powerful way when a pair of lesbians in rural Massachusetts befriended their state representative and helped change his mind about the issue. In another case, when their research found that a certain lawmaker loved musicals, the campaigners got the author of Wicked to write him a personal letter comparing the main character’s underdog struggle for acceptance with the situation gay people faced.

Solomon’s book is full of colorful tales of this kind of creative political blocking and tackling. Some of this stuff—applying grassroots pressure, lobbying key lawmakers personally—is Politics 101, but progressive causes haven’t always been good at it. Another of the lessons from the marriage fight is that you have to play the political game and play it well; when what you want is change, there is no alternative.

The MassEquality campaigners saw to it that every single legislator who voted their way got reelected, while some who didn’t were targeted and ousted—including a virulently homophobic member of the state House’s Democratic leadership, who lost a primary to a young openly gay man with no political experience. Solomon moved on to help with the campaign for gay marriage in the New York state legislature; there, after losing a big vote in 2009, campaigners helped take out some of the Democrats who’d broken their promises to vote their way. “In the early days of this fight, our community had zero political power,” Solomon told me. “When they saw us mobilize, raise money, engage in elections, save some lawmakers and knock out others—that’s when [politicians] started taking us seriously.”