Special elections to the California State Senate are called by the Governor of California when a vacancy arises within the State Senate. Special elections are conducted in two rounds. The first round is an open primary. The second round is cancelled if one of the candidates receives more than 50% of the vote in the first round. Prior to 2012, the top vote getter from each party in the first round would advance to the second round. Since the passage of Proposition 14 in 2010 (which became effective 2012), the top two vote getters in the first round, regardless of party, advance to the second round.
Recall elections, the process by which voters petition for the removal of an elected official, are also included.
The dates listed indicate the time of the final election, either a runoff election or the open primary round if no second round was held.
A replacement state senator is only listed in cases in which the recall was successful.
The first round of the special election was consolidated with the regularly scheduled primary election. Although most of the candidates in the two contests were the same, the results were very different. Rita Topalian finished first in both races, but different candidates finished in second place. Vanessa Delgado finished in 2nd place in the special election, but 3rd place in the regularly scheduled primary election. She received a similar number of votes in both races, but candidate Bob Archuleta received about 54% more votes in the regularly scheduled election than he did in the special election. The different results have been attributed to the different order in which the candidates were listed on the ballot.
Incumbent Republican Janet Nguyen resigned after winning a seat for the Orange County Board of Supervisors. A special election was held on February 25, 2025 to fill the vacancy.