Each political party has the option of allowing people who register to vote without stating a political party preference ("no party preference" voters – formerly known as "decline-to-state" voters) to vote in their presidential primary election. A political party must notify the Secretary of State's office whether or not they will allow no party preference voters to vote in their presidential primary election 135 days before the election.
If a no party preference voter wishes to vote in the presidential primary election of a political party who has notified the Secretary of State that they will allow no party preference voters to vote in their party’s primary, a no party preference voter would simply ask their county elections office or ask a poll worker at their polling place for a ballot for that political party. A voter may not request more than one party's ballot.
If a no party preference voter does not request such a ballot, they will be given a nonpartisan ballot, containing only the names of candidates for voter-nominated offices and local nonpartisan offices and measures to be voted upon at that presidential primary election.
A "closed" primary system governed California's primary elections until 1996. In a closed primary, only persons who are registered members of a political party may vote the ballot of that political party.
The provisions of the "closed" primary system were amended by the adoption of Proposition 198, an initiative statute approved by the voters at the March 26, 1996, Primary Election. Proposition 198 changed the closed primary system to what is known as a "blanket" or "open" primary, in which all registered voters may vote for any candidate, regardless of political affiliation and without a declaration of political faith or allegiance. On June 26, 2000, the United States Supreme Court issued a decision in California Democratic Party, et. al. v. Jones, stating that California's "open" primary system, established by Proposition 198, was unconstitutional because it violated a political party's First Amendment right of association. Therefore, the Supreme Court overturned Proposition 198.
California's current "modified" closed primary system for Presidential elections was chaptered on September 29, 2000 and took effect on January 1, 2001. Senate Bill 28 (Ch. 898, Stats. 2000) implemented a "modified" closed primary system that permitted voters who had declined to provide a political party preference (formerly known as "decline to state" voters) to participate in a primary election if authorized by an individual party's rules and duly noticed by the Secretary of State.
On June 8, 2010, California voters approved Proposition 14, which created a "top two" or "open primary" election system.
Except for the office of U.S. President and county central committee offices, offices that used to be known as "partisan offices" (e.g., state constitutional offices, U.S. Congress, and state legislative offices) are now known as "voter-nominated" offices. What used to be known as a "political party affiliation" is now known as a "political party preference."
Prior to the Top Two Candidates Open Primary Act, all candidates running in a primary election, with the same political party affiliation, were placed on a partisan ballot to be voted on by voters of the same political party. The top vote-getter from each qualified political party would move on to the general election. At the general election, candidates could gain access to the ballot using the independent nomination process and other could run as write-in candidates.
Under the Top Two Candidates Open Primary Act, all candidates running in a primary election, regardless of their party preference, will appear on a single primary election ballot and voters can vote for any candidate. The top two overall vote-getters – not the top vote-getter from each qualified political party – will move on to the general election. Additionally, candidates are no longer allowed to run as "independents" or "write-ins" at the general election.
Prior to the Top Two Candidates Open Primary Act, a candidate for a partisan office would have the political party they were registered with listed next to or below their name on the primary and general election ballots. A candidate who won at the primary election was then considered to be the official nominee of their political party.
Now, under the Top Two Candidates Open Primary Act, candidates for voter-nominated office must indicate their party preference or lack of party preference on the primary and general election ballots. Political parties can no longer formally nominate candidates for voter-nominated offices, so a candidate who finishes in the top two at the primary election and advances to the general election is not the official nominee of any party for the office.