"It's a real challenge, since you're really running two elections simultaneously," said Jim Stearns, consultant for state Sen. Leland Yee's run for mayor. "Normally, in a primary you have to identify your base, organize and get them out to vote. But in a ranked-choice election, you have to get beyond your base and identify other potential supporters."
Under ranked choice, if no candidate collects a majority of the first-choice votes in the first round, the candidate with the fewest votes is dropped from consideration and his second-choice votes are added to the totals of the remaining candidates. This continues, round after round, until someone crosses the 50 percent mark.
"All of a sudden, we're talking about seconds and thirds," said John Whitehurst, a political adviser to City Attorney Dennis Herrera's campaign for mayor.
Because each voter can choose three candidates on the ballot, many of the city's dozens of endorsing groups are listing three names, too. That opens the door for Herrera and other candidates to get a second- or third-choice nod from groups where they would never be the first pick.
"In a regular election, we'd normally go after four or five endorsements," Whitehurst said. "Now we go after everything because the cumulative effect can make a difference."