It's called ranked choice voting or instant runoff voting and it's been around for a while. Other countries use it. Cities in the United States use it. The State of Maine might be using it for all of its state-wide elections. Even the Academy Awards use it.
https://en.wikipedia.org/wiki/Instant-runoff_voting
https://en.wikipedia.org/wiki/Instant-runoff_voting
So how does it work? Easily.
Instead of voting for just one person, you rank multiple candidates. For example, under ranked choice voting, a presidential ballot could look like this:
1. John Kasich
2. Michael Bloomberg
3. Jeb Bush
4. Gary Johnson
5. Bernie Sanders
Or some other combination.
Try it yourself. Go back to that experimental ballot we discussed earlier and rank five candidates, or just four, or three, or two, whatever. Put them in order from your favorite to least favorite. Ok. That's your ballot. You just voted under ranked choice voting. How easy was that? Really easy.
After all, you rank everything else. Before you go to a restaurant, you rank what you want to eat in case the restaurant is out of your first choice. You rank sports teams. You rank movies you want to see. You can't go five minutes on the internet without a "ten best" list popping up. You rank everything - it's how our brains work. So why not rank our politicians?
With ranked choice voting, we can. And it's way better than this archaic voting method we use now.
How we vote now is like playing football with leather helmets. It's like playing golf with a wooden shafted clubs. It's like using a road map instead of GPS. It's outdated.
With ranked choice voting, we can express our full preference of the candidates rather than just picking one person. So what do we do with all of these ballots? We count them.
https://rcv-sc.blogspot.com/2017/11/how-it-works.html