Why it matters: The state has been a Democratic stronghold for nearly four decades, and that's likely to remain the case in this election with Vice President Kamala Harris, who came up in California politics.
Zoom in:San Diego County last voted for the Republican ticket in 2004, when George W. Bush and Dick Cheney were re-elected.
State of play: The Harris campaign leads former President Trump 60% to 29%, according to a September survey of likely voters by the Public Policy Institute of California.