Targeting for the upcoming San Diego mayoral Special Election is complicated because San Diego provides few recent examples from which to create a likely voter turnout model. There are statewide special elections in 2003, 2005 and 2009, and there were recent special elections in portions of the city – Council District 4, SD 40 and AD 80 – but these turnout rates may not be indicative of voter performance in a high-profile Mayoral Special
The last citywide special was the 2005 Mayoral Special election to replace Dick Murphy. The overall turnout from the Special Primary was 50% and the runoff (which was combined with the Statewide Special Election) saw 57% turnout.
The following data from archived PDI Voter Files from 2005 show turnout rates for each subgroup, and then the rates of turnout in each of the old council district boundaries.
The breakdown by council district shows the lowest turnout from the old Council District 8 which had 52% Latino registration and the second-lowest turnout from District 4 with 25% Latino registration. Non-partisans in these two districts showed a turnout rate at nearly half that of the overall electorate.
The Republican turnout rates were six-points over base turnout in both the Primary and Runoff, with a sky-high 63% Primary and 67% Runoff turnout in old Council District 6. However, as can be seen in the next set of data, Republicans were a slightly lower overall share of the electorate in both the primary and runoff.
These turnout rates are one piece of the puzzle, but just as important is how the changes in turnout from a General Election to a Primary or a Special change in terms of shares of the electorate. What share of the voters are Democrats or Republicans, what share of the voters are Latino or Asian?
For the 2005 Primary election the registered voters were 39% Dem, 34% Rep and 27% independent. 13% of the voters had a Latino surname while 7% had an Asian surname. As can be seen in the following chart, Latinos, Asians and Non-Partisans under-performed slightly while partisan voters turned out in slightly higher numbers.
The runoff, with the same registered voter breakdown as the Primary, saw a slight resurgence among Latinos, A small uptick for Democrats and Independents, and a couple-point drop for Republicans. Essentially, higher turnout from Latinos and less-frequent voters resulted in a gain for Independents and Democrats, albeit very small.
While this 2005 recall election had turnout similar to a statewide primary election, looking at just the recent turnout for Assembly, Senate and City Council special elections would paint an entirely different picture. The San Diego City portion of the AD 80 contest was only 23% turnout, and SD 40 overlap was just 13%. The Recent city council District 4 special election was at 20%. Using these elections to build a turnout model would likely cause a campaign to significantly under-predict turnout.