California Code, Elections Code - ELEC § 8203

(a) In any county in which only the incumbent has filed nomination papers for the office of superior court judge, his or her name shall not appear on the ballot unless there is filed with the elections official, within 10 days after the final date for filing nomination papers for the office, a petition indicating that a write-in campaign will be conducted for the office and signed by at least 0.1 percent of the registered voters qualified to vote with respect to the office, provided that the petition shall contain at least 100 signatures but need not contain more than 600 signatures.

(b) If a petition indicating that a write-in campaign will be conducted for the office at the general election, signed by the number of registered voters qualified to vote with respect to the office specified in subdivision (a), is filed with the elections official not less than 83 days before the general election, the name of the incumbent shall be placed on the general election ballot if it has not appeared on the direct primary election ballot.

(c) If, in conformity with this section, the name of the incumbent does not appear either on the primary ballot or general election ballot, the elections official, on the day of the general election, shall declare the incumbent reelected.  Certificates of election specified in Section 15401 or 15504 shall not be issued to a person reelected pursuant to this section before the day of the general election.