When Iowa Democrats hold their February 2020 presidential caucuses, millions of Californians will already have their primary ballots.

The nation’s most-populous state has moved its primary to March 3, 2020, so it can have more influence in picking presidential nominees. The move from a June primary in 2016 will press hopefuls to consider a West Coast perspective on issues such as immigration and the environment, empower the state’s growing Latino and Asian populations and drastically increase the amount of money candidates...