California Code, Elections Code - ELEC § 9602

A voter who has signed an initiative or referendum petition, and who subsequently wishes their name withdrawn, may do so by filing a written request for the withdrawal with the appropriate elections official that includes the name or title of the petition and the voter's name, residence address, and signature. This request shall be filed in the elections official's office prior to the date the petition is filed. A written request made under this section shall not constitute a petition or paper for purposes of Section 104.