Reply #4: It depends on where you live

[DFLforever]

In Minnesota you NEVER are required to declare a party affiliation - either at the time you register or when you vote, whether in a general or primary election. All voters get the same ballot but in a primary election (unlike the general election) you cannot split your vote among parties - to do so invalidates the ballot. MN no longer has a presidential primary but instead uses a caucus system where the party specifies requirements for participation.

edited for clarity