In addition to the U.S. presidential race, California voters elected one member to the United States Senate, all of California's seats to the House of Representatives, all of the seats of the State Assembly, and all odd-numbered seats of the State Senate.

Incumbent Barbara Boxer did not seek re-election, which makes this the first open Senate seat election in 24 years in California.

The increase has been attributed to the relatively low number of signatures required for ballot placement for this election.

The number of signatures required for ballot placement is a percentage of the turnout in the previous election.

Since the turnout in the November 2014 elections was low, the number of signatures required for ballot placement in 2016 was 365,880, whereas the typical requirement is well over half a million signatures.