In California’s top-two primary for state and congressional elections, all candidates are listed on a single ballot, and the two who receive the most votes, regardless of party, advance to the November election.
California voters decided in 2010 to switch to the open primary system, where voters aren’t limited to choosing among candidates from their own parties. (The ballot measure didn’t change the rules for nonpartisan offices or for presidential primaries, where the qualified parties have their own rules.)
In some races — L.A. County supervisor, sheriff or L.A. mayoral contests, for example — if a candidate gets even one vote over 50% in the primary, he or she wins outright.