Allows voter to vote in any political party primary by changing party affiliation at polling place on primary election day; allows mail-in voter to complete any political party primary ballot.

S 390 (New Jersey) allows voters to change their party affiliation at the polling place on primary election day or by submitting a different party's mail-in ballot. This changes existing rules that required voters to declare a party affiliation 55 days before a primary. Voters who sign a declaration at the polls or return a different party's mail-in ballot become members of that party for the election. The bill directly affects all New Jersey voters participating in primary elections, removing the previous 55-day deadline for party affiliation changes. It amends election law sections to enable same-day party switching for in-person and mail-in voters.