How Ranked-Choice Voting Upends Elections

Using our exclusive simulator, The Bay Citizen dissects the surprising results of recent Bay Area votes

On Tuesday, San Francisco voters will be asked to use a controversial election system known as ranked-choice voting. The process is simple enough: select your first-, second- and third-choice candidates for mayor, district attorney and sheriff. But history shows that the results are anything but predictable. Using our exclusive ranked-choice voting simulator, The Bay Citizen dissected two recent Bay Area elections that were turned upside down by this alternative voting system: Oakland's 2010 mayoral race and San Francisco's 2010 District 10 supervisorial election.

In the Oakland mayoral election, former state Sen. Don Perata held a commanding lead over nine other contenders, but he unexpectedly lost to underdog Jean Quan, then an Oakland City Council member, in the final round of vote tabulation. Perata had started with 33 percent of first-choice votes — well short of the majority needed to win outright. The ranked-choice calculation began, and for nine rounds, he remained in front. At the end of each round, a candidate was eliminated, and the second or third choices of the voters who had selected the dropped candidate were redistributed. In the ninth round, Perata had 10,000 more votes than Quan, who illustrated the dynamic power of ranked-choice voting by staging an extraordinary comeback to win the mayor's office.

When the 10th round ended, it became clear that Quan had cannibalized 18,000 second- and third-choice votes from City Council member Rebecca Kaplan — just enough to trip over Perata’s lead by a mere 2,025 votes and upset the race. Click through the simulator below to see the round-by-round results.

In Part II, see how a couple thousand voters could have handed Perata the victory.