“Lots of people don't fill out all the choices” is an important downside. We’ve had Instant Runoff Voting in San Francisco since 2004, and people still don’t fi

“Lots of people don't fill out all the choices” is an important downside. We’ve had Instant Runoff Voting in San Francisco since 2004, and people still don’t fill out all the choices, so their votes are discarded whereas the voters probably would have voted among the final two choices had there been a runoff election. For example, in June 2018 London Breed won the mayoral election against two candidates who were closer aligned politically (Jane Kim and Mark Leno, who were further left) https://dbaron.org/sf-elections-rcv/#%7B%22election%22%3A%2220180627%22%2C%22filters%22%3A%5B%5D%7D https://dbaron.org/sf-elections-rcv/#%7B%22election%22%3A%22... and in Nov 2019 Chesa Boudin won the District Attorney race against 3 candidates who were more moderate https://dbaron.org/sf-elections-rcv/#%7B%22election%22%3A%22CVR_Export_20191125163446%22%2C%22filters%22%3A%5B%5D%2C%22contest%22%3A%22339%22%7D https://dbaron.org/sf-elections-rcv/#%7B%22election%22%3A%22... . In both cases, the margin of victory was far more narrow than the number of votes that were exhausted in the final round of voting, so due to insufficient voter education I would consider vote splitting still a significant problem even with IRV. (Another possibility is that the ballots are exhausted by the 3 candidate limit in San Francisco.)