The fraudulent study called into question the validity of the Leadership Lab’s deep-canvassing approach. Had it all been wishful thinking? Maybe, as The Wall Street Journal suggested, Fleischer’s efforts merely “flattered the ideological sensibilities of liberals.” But this week, a new study published in Science by David Broockman, an assistant professor of political economy at Stanford, and Joshua Kalla, a graduate student in political science at Berkeley, appears to serve as vindication of Fleischer’s work. Leadership Lab-trained volunteers were found to be successful at reducing transgender prejudice in front-door conversations, the effects persisting months later in follow-up surveys.

Betsy Levy Paluck, an associate professor at Princeton who studies bias, believes the study will have broad implications for those in her field. “What do social scientists know about reducing prejudice in the world? In short, very little,” she writes in the same issue of Science, adding that the new study’s results “stand alone as a rigorous test of this type of prejudice-reduction intervention.”

Fleischer is planning more interventions. Though he has devoted much of his political and community-organizing career to L.G.B.T. issues, he believes this kind of canvassing could change people’s thinking on everything from abortion and gun rights to race-based prejudice. He also hopes it will usher in a new era of political persuasion. “Modern political campaigns have focused mostly on communicating with people who already agree with them and turning them out to vote,” Fleischer says. “But what we’ve learned by having real, in-depth conversations with people is that a broad swath of voters are actually open to changing their mind. And that’s exciting, because it offers the possibility that we could get past the current paralysis on a wide variety of controversial issues.”

It took a devastating loss at the ballot box for Fleischer to see the political wisdom in heart-to-hearts with strangers. In 2008, he was in Ohio mobilizing African-American and Latino voters for Barack Obama when California residents passed Proposition 8, banning same-sex marriage in the state. Fleischer headed west to work with the Los Angeles L.G.B.T. Center, which houses the Leadership Lab, and proposed an unusual idea to his new colleagues: Canvassers should talk to Prop 8 supporters about why they had voted against same-sex marriage. Then they should try to change the voters’ minds.

The idea grew out of Fleischer’s own experience as a “Jewish, liberal gay kid” in Chillicothe, Ohio. He likes to say that he has been talking to people who disagree with him since he was 4. “If I would have only talked to people who agreed with me, I would have only talked to my mom and dad,” he told me. “Interacting with people different than me was a normal thing, and certainly not undesirable or scary. It’s almost the opposite of growing up today in the age of Facebook and political polarization, where it’s easy to always be among like-minded people, your self-isolation complete before you have your first beer.”

At first, Fleischer and his team tried cerebral arguments and appeals to fairness in their doorway conversations with same-sex-marriage opponents who didn’t express deep religious objections. “That failed miserably,” he said. Eventually, the canvassers tried eliciting more emotional experiences. They urged voters to talk about anyone they knew who was gay or lesbian — and, more important, to speak about their own marriages. “That changed everything,” Fleischer told me. “Most people consider marriage the most important and meaningful thing they ever did. Talking about marriage brought up deep emotion. If marriage was the most valuable thing in their own life, wouldn’t they also want their gay friends — or gay people — to experience it, too?”