Tuesday’s San Francisco mayoral election was a landmark moment for American democracy—and not just because the three leading candidates to lead a bellwether city were a black woman, a Korean-American woman, and a gay man. It appears likely to be the largest election in recent U.S. history in which the candidate with the most first-choice votes didn’t win.

Mark Leno, the 66-year-old state senator who is currently on his way to winning, is a pretty likable guy. He’s progressive, but with more remove from city politics than Supervisor Jane Kim, who finished third. He’s an old-timer, but without the reputation for the status quo of Board of Supervisors President London Breed, who appears to have finished second. (The votes are still being counted.) In a Goldilocks, low-turnout election with three front-runners, he won because most San Franciscans thought not “Hey, that guy’s just right,” but that he’s just all right.

How did this happen? San Francisco employs an uncommon voting model, popular among political-science academics, known as “ranked-choice” or “instant runoff” voting, in which votes to trailing candidates are progressively reassigned to their voters’ second- or third-choice candidates, which they indicate on their ballots. In this model, there is no such thing as “wasting” a vote.

As of Wednesday morning, the race was too close to call, but Leno held a narrow lead over Breed, 50.42 to 49.58 percent. That’s a big change from the first round of the vote, when Breed held a 10-point lead over Leno, 35.6 to 25.9.

Breed’s lead was shrinking but solid until Kim, who finished third with 22.8 of first-place votes, had her voters reassigned. More than 3 in 4 went for Leno, reflecting the candidates’ similar views—and the success of a strategy in which the two candidates who otherwise split the city’s left-wing block explicitly asked their voters to pick the other as a second choice.

The candidates did not easily fit into neat boxes. Breed, the establishment favorite and the moderate, was the only native San Franciscan in the group, but also the rare candidate not to blame the city’s problems on newcomers. Kim, a transplant whose Manhattan upbringing was the subject of a miniscandal when she published leading questions asked of her by the San Francisco Chronicle, was arguably the most vocal about the need to enhance the safety net. Leno promised to “shake up City Hall,” but at 66 he’s been involved in politics longer than Breed and Kim put together. (He did have the advantage of being insulated from controversial local issues during 14 years in the statehouse.) Like outgoing Gov. Jerry Brown, he’s an example of Californian progressive nostalgia, looking forward by looking backward.

If it holds, the result would mirror a 2010 ranked-choice election in Oakland, in which Jean Quan (also coming from the left) vaulted over front-runner Don Perata in a crowded field, despite trailing him by double digits as a first choice.

Would the result have been different if, instead of using ranked choices to eliminate candidates, San Francisco employed a runoff election, in which top candidates went to another vote? Quite possibly. A runoff candidate with more first-choice votes (in this case, Breed) would probably generate more enthusiastic turnout than a candidate who vaulted to the top as a second or third choice (in this case, Leno).

During the campaign, the San Francisco press played the possibility of a Leno-Kim-alliance victory as a political revolution, the chance to end what the San Francisco Chronicle called a “moderate-led executive branch dynasty” that has overseen decades of rapid jobs growth but little new housing. But if it’s a revolution, it’s one of shallow, widespread consensus, not of the kind of deep and passionate support that can push a radical to the fore.

While Leno may not represent the status quo, he does represent an emerging anti-tech, anti-market-rate-development consensus that has been building for years. It may have been slow to manifest in the mayor’s office because the 2015 mayoral election featured well-liked incumbent Ed Lee. But it was already well-represented on the board of supervisors, which in an effort to reduce Breed’s advantages in the mayoral race, removed her from the interim job in January. (There were good reasons to do so, but boy, did it look bad.)

Tuesday is an example how the system, which is being considered for Maine’s state and federal elections, is supposed to work: to encourage alliances, coalition-building, congeniality, and wide fields. More polarizing candidates get eliminated in favor of a moderate outcome. Whether this is a good thing or not is another question.