On June 5, the California Secretary of State released the number of ballots still uncounted from the June 3, 2014 primary. That number is 1,011,398. When that figure is added to the number of votes cast for Governor that had been counted as of the same point, 3,296,369, the sum is 4,307,767. The number of registered voters in California just before the primary was 17,722,006. This yields a 24.3% turnout.
Not all of the uncounted ballots will be valid, because many of them are provisionals, and most provisional ballots are found invalid, because the person who cast that vote wasn’t registered to vote. On the other hand, there are some ballots which invariably were blank for Governor.
The previous lowest primary turnout in California history was the June 2008 primary, which had turnout of 28.2% turnout. That primary had no statewide offices on the ballot, because the presidential primary had been held in March 2008.