For Republicans, election rules keep things in the party. You must be a registered Republican to vote for a Republican presidential candidate. The California Democratic Party is more lenient, allowing no-party-preference voters to help choose its nominee.

There’s a catch, however. Primary election ballots landing in the mailboxes of partyless voters do not include presidential candidates. For that, they’ll need to specifically request a Democratic primary ballot or show up to vote in person. Mailing in the ballots that don’t contain presidential candidates would prevent them from also voting in the presidential primary.