Ranked-choice voting, also called "Instant Run-off voting", is a way to provide voters more meaningful choices on the ballot, while avoiding the negatives of traditional run-off elections.
The "first past the post" method of determining a winner is that whoever gets the most votes in the general election is declared the winner, even if they get less than fifty percent of the vote. In practice, this means that people are afraid to vote for third party candidates or independents out of fear of "splitting the vote" and allowing the party they hate to sneak in with less than a majority of the vote. The two establishement parties don't even have to sell themselves anymore, just demonize the other side so that their base is terrified of what will happen if the "other side" wins. No matter how corrupt they get, their base feels compelled to make excuses for them, because the alterantive is the-end-of-the-world.
The solution is to have run-offs so that people can vote their conscience without fear. If the dominant party they favor goes corrupt, they don't have to keep voting for them. They can vote for a third party or independent in the general election to send a message that the major party better clean up its act. This would not result in throwing the election to the other party because if no one gets over 50% of the vote, there is a run-off election where the voter can then cast their vote for whoever else is left.
This kind of freedom is viewed with great alarm by Republicans and Democrats alike. They are "bi-partisan" in their belief that voters should be terrified into voting for them even if another candidate seems like a better choice.
Sarasota Florida and Memphis Tennessee decided to use ranked-choice voting for their city elections. It should be their business, right? Despite citizen overwhelming citizen support for Ranked Choice Voting in both cities, even against the oppostion of political "leaders", the state legislature off both states have passed laws making the practice illegal.
The two dominant parties want to force Americans into voting for one of them or not at all. That way, it doesn't matter that they don't represent you and you know it. They only have to be slightly less repulsive than the only other choice.