California Code, Elections Code - ELEC § 6061

Any unselected candidate or uncommitted delegation desiring to be placed on the presidential primary ballot shall have nomination papers circulated on behalf of the candidacy. In order to qualify for placement on the presidential primary ballot, the candidate's or uncommitted delegation's nomination papers shall be signed by voters registered as affiliated with the Democratic Party equal in number to not less than 1 percent or 500, whichever is fewer, in each congressional district of the number of persons registered as members of the Democratic Party in the report of registration issued by the Secretary of State on the 135th day preceding the presidential primary election.

The unselected candidates or uncommitted delegations shall meet the statewide signature requirements from each congressional district in order to be eligible for placement on the ballot in any one congressional district.