Data and Maps From the 2018 San Francisco Mayoral Election

Posted by Pedro Hernandez on July 31, 2018

Assembled Data and Maps of the 2018 San Francisco Mayoral Election


Final Round Breed v. Leno by Precinct

This is a follow up to our previous reporting on the 2018 San Francisco Mayoral Election.

The San Francisco Department of Elections releases several detailed files of public data on ranked choice voting (RCV) contests. These files include a Summary Report, a Statement of Vote, Ranked Choice Voting Results Table, and well as a Ranked-Choice Voting Ballot Image file. This ballot image file contains an anonymized record of ballots cast, which many researchers use to study the effect of RCV as an electoral reform. The public has access to these files, and some have already audited the accuracy of the count. 

However, many initial reports of the mayoral election only reported the first-choice accounting of the election, as reported in the Statement of Vote. Such reporting offers only a snapshot of how the candidates fared in the first round of the RCV contest. Here, using ballot image information, we dive deeper into the final round count by district and precinct. 

Click here to access a google sheet document of final round district and precinct information. 

Final Round By Districts

In terms of districts, London Breed did win a majority of districts: Six. 

Breed won in Districts 2, 4, 6, 7, 10, and 11. Leno won in Districts 1, 3, 5, 8, and 9.

District 10 offered Breed the largest margin of victory over Leno where she led Leno by 3,985 votes in the final round. 

Board of Supervisors District Breed Final Round Vote Leno Final Round Vote  Winner 
1 9929 10143 Leno
2 12635 9435 Breed
3 7949 8674 Leno
4 10055 8485 Breed
5 13454 13690 Leno
6 8141 7473 Breed
7 12844 10459 Breed
8 14229 20012 Leno
9 8560 12099 Leno
10 10115 6130 Breed
11 8066 6831 Breed
Total 115977 113431 Breed

However, the biggest surprise is that Mark Leno narrowly won in District 5, which is Mayor London Breed's supervisorial district. Initially, Breed received 11,270 of first choice support in District 5, followed by Jane Kim who received 8,101 first choice votes. Mark Leno came in third with 6,908 first choice votes in the District. When Jane Kim was eliminated in the city-wide RCV count, Leno picked up 6,782 votes from supporters of Jane Kim and other defeated candidates. Leno then led with 13,690 votes to Breed's 13,454. 

In District 8 delivered the biggest margin vote to Leno. Initially, Leno he led with 12,731 first choice votes, he then picked up 7,281 additional votes from supporters of other candidates, mainly Jane Kim. Of Jane Kim’s 8,232 votes in District 8, 84% of those ballots who indicated another preference went to Mark Leno in the final round. Leaving Leno with  20,012 votes in District 8. 

Final Round By Precinct

Overall, London Breed won 320 out of 596 precincts, Mark Leno won 271, and five precincts were tied. Breed fared well across the city and gained deep support from west side, Western Addition, Marina, and Bay View/Hunters Point voters. 

Those who follow elections closely may note that there are 604 precincts in San Francisco. However, some of these precincts had no votes cast, and most of these no-vote precincts are public parks. 

Precinct Maps

First Choice Support for London Breed


First Choice Support for Mark Leno


First Choice Support for Jane Kim


Final Round Breed v. Leno


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  • Pedro Hernandez