Maine passed it recently for all it's statewide elections. NYC just passed it, joining several other communities. You rank your choices of all the candidates in the order you want them. All ballots are tabulated the first time and if no one gets more than 50% they drop the candidates with the lowest total of 1st place votes and then they distribute votes for their second place candidate. After another retabulation of votes they can check to see if anyone gets 50% and if not, they drop the next person with the lowest total, rinse, repeat until someone meets the threshold. This eliminates strategic voting and ultimately delivers the will of the people. Conservatives don't seem to like it because the electorate is getting more and more progressive by the day and these systems tend to deliver more progressives like today in SF where the candidate that Bernie endorsed for D.A. just surpassed the establishment candidate in the tabulation. One of the Republican congressmen in Maine filed a lawsuit because he got voted out. He claims RCV is not constitutional. He lost and decided not to appeal to SCOTUS.