Ranked-choice voting, explained

What if I told you that instead of voting for just one candidate in the next election, you could vote for several — ranking them in order of your preference?

Registered Democratic voters in New York City are getting that opportunity. Their mayoral primary on June 22 will be the city’s first to use ranked-choice voting — and that race will be the biggest spotlight yet for this system in the United States.

Ranked choice is the reform of wonky activists’ dreams. They believe that more traditional elections, where whoever gets...