California voters chose electors to represent them in the Electoral College via a popular vote, pitting the Republican Party's nominee, businessman Donald Trump, and running mate Indiana Governor Mike Pence against Democratic Party nominee, former Secretary of State Hillary Clinton, and her running mate Virginia Senator Tim Kaine.

On June 7, 2016, in the presidential primaries, California voters expressed their preferences for the Democratic, Republican, Green, and Libertarian, Peace and Freedom, and American Independent parties' respective nominees for president.

Five candidates appeared on the Republican presidential primary ballot, four of whom had suspended their campaigns prior to the primary:[5] Donald Trump, the only candidate with an active campaign, won each Congressional district by substantial margins, as well as all the statewide delegates, to capture all 172 votes.

The American Independent Party nullified the results of this primary when they endorsed Donald Trump in August.

The average of the last three pre-election polls showed Hillary Clinton leading Donald Trump 54.3% to 32%.

Donald Trump received 31.6% of the vote, making for a Democratic victory margin of 30.11 points.

[28] The California state result was historically one of the most successful for the Democratic Party nominee by several measures, as Hillary Clinton carried California by the largest margin of any Democratic candidate since Franklin D. Roosevelt swept the state by 35.25% in his 1936 re-election landslide.

[30][31] California was the only large state (one with at least 15 electoral votes[32]) in which Hillary Clinton lost no counties that had been carried by Barack Obama in 2012.