Most San Franciscans probably don’t realize that something on their ballot is revolutionary. It’s not a candidate or a ballot proposition—it’s a a style of voting.

If you’re not that interested in the mechanics of voting, I hear you. My favorite political subjects are meatier, spicier, juicier—insert-your-favorite-food-metaphor-here.

But more often than I’d like, the most transformative policies aren’t about banning some terribly corrupt behavior or exposing some nefarious wrongdoing. They’re about changing rules that, in turn, change the incentives of political elites.

A couple examples:

Give every voter a small voucher they can only spend on elections, and—surprise, surprise—politicians suddenly engage way more with typical voters, not just big-money donors.

Move all elections to the same day (rather than staggering them across the year), and turnout is higher—which means small, engaged interest groups have less say over election outcomes.

Political scientists and policy geeks like me call these institutional reforms. Back in 2002, San Francisco voters bypassed the city council (we call it the “Board of Supervisors”) and passed one themselves. The reform is called “ranked choice voting,” or RCV.

Please, don’t stop reading.

You can read a million and one explanations of RCV online, but I’ll spare you that less-than-thrilling Google search. Basically, ranked choice voting is exactly what it says. Instead of choosing one candidate, you rank your choices: first place, second place, and third place.

(SF only lets you rank three choices, but other places let you rank all the candidates. Not important here.)

Here’s how the rankings get used. The vote-counters in City Hall (hello, you guys! keep up the good work!) count up all the first-place votes, and one of the candidates comes in last. Say it’s the person that you put at the top of your list, the person you really want to win.

Under an old-school voting system, that’s it; your vote was essentially wasted. In fact, it hurt the chances of your second-place candidate. They‘re more popular and have a better chance of winning the overall election, but you used up your vote on someone else.

(By the way, this is a really common problem, and it leads people to vote in ways that don’t reflect what they truly want. If you know that the Democratic nominee and the Republican nominee will always win, then why “waste” your vote on an outside candidate, even if you like them more?)

So, back to the world with RCV. Your favorite candidate came in last; that’s sad. However, it’s not that sad, because RCV has a solution.

The good ol’ vote-counters at City Hall tally up the votes. If no one is a clear winner (i.e. gets more than 50% of the vote), they drop the candidate who got the lowest number of first-place votes.

Because your first-place candidate got dropped, your vote gets redistributed to your second-place candidate. (This process keeps going, with candidates getting eliminated and votes getting redistributed until one of the candidates has more than 50% of the vote.)

Your vote wasn’t wasted! You didn’t jeopardize the chances of your next-favorite candidate! It’s basically like you had a chance to come back to the voting booth and say, “OK, my favorite person isn’t in the running anymore, so here’s my next choice.” But by ranking people up-front, you save a trip, and the city saves money from not having to hold a second (or third, or fourth) election.