Major political parties (Democratic and Republican) nominate their candidates at a primary election, which is held on the third Tuesday in May of each even-numbered year. Only a voter who is registered as a member of either political party may vote for that party's candidates at the primary election unless the party opens its primary to voters registered as Not a member of a party. If this is the case, voters who are Not a member of a party must request major party ballots from their county elections office.
Most nonpartisan offices are also on the primary election ballot. Any registered voter may vote for those candidates, regardless of the voter's political party affiliation.