Cal. Gov. Code § 20096.3

If an incumbent member of the board, holding a board seat described in subdivision (g) of Section 20090, does not deliver his or her completed nomination documents to the election coordinator for reelection by the applicable filing deadline for candidates for the seat, any otherwise eligible person other than the person who was the incumbent on the filing deadline shall have until 10 days after the filing deadline to file nomination documents for the same office. This section is not applicable if there is no incumbent eligible to be elected or if the notice of election states that the incumbent does not intend to be a candidate for reelection.