How does ranked-choice voting work?

Let’s say I’m throwing a party for 100 people. Since I’m a really considerate host, I want to let my guests vote on what flavor of ice cream we’ll have for dessert. I give them four options: chocolate, vanilla, strawberry, and peanut butter. What’s the best way to take everyone’s opinion into account? One option is plurality voting, also called “single choice” or “winner-take-all.” This one is easy for me as the host, since all I have to do is choose the flavor that gets the most votes. Here, peanut butter got the highest number of votes—but the majority of my guests didn’t vote for it. And if anyone is allergic to peanut butter, this voting method didn’t really take the gravity of their needs into account. Maybe I should try alternative voting, also called “ranked choice.” In this method, I ask everyone to rank the options in order of preference. And a flavor can’t win until it gets more than half the votes. Right now, no flavor has 51 votes. So what I’m going to do is kick the lowest-ranking option out of the running. But I still want people who ranked vanilla highest to have a say, so their votes are redistributed to their second choice. I still don’t have a majority, so we’re going to remove the least-popular option again and redistribute the votes. We’ll keep repeating this process until a flavor gets 51% of the votes. So it turns out that the majority of my guests prefer chocolate ice cream over peanut butter—something I would never have known if I’d had people only select their first choice. Is this the fairest method to decide on an ice-cream flavor? Some guests might want me to try something called condorcet voting, which matches each flavor against every other option. The flavor that wins the most head-to-head matches is the overall victor. That seems like a lot of work for me as the party’s host… Okay, I’ll admit it. The ice-cream party was just a ploy to talk politics. These are real voting methods that are used in different types of elections across the world. Most elections in the United States, including presidential elections, are examples of plurality voting: voters pick one candidate out of a few options and can’t indicate a second or third choice. Ranked-choice voting has started to become more popular, especially in the mayoral elections of large cities like New York and San Francisco. This can encourage like-minded candidates to work together: “Hey, if you like me, you may want to rank my friend here second!” As for condorcet voting, it’s more theory than practice right now. Proponents say it’s the fairest way to vote—but most legal experts say that every voting method can be a little unfair to someone. Just look at me, I voted for vanilla.