20 states have open primaries, including South Carolina. On primary election day you get to pick which party's primary you want to vote in. Usually the more exciting primary is chosen, which in this case is the GOP primary, because the Dem primary is a foregone conclusion for Brandon.
Other states, including NY, are closed primary states where they have voters register by party. Then on primary election day you can only vote in the primary if you registered with that party in advance.
20 states have open primaries, including South Carolina. On primary election day you get to pick which party's primary you want to vote in. Usually the more exciting primary is chosen, which in this case is the GOP primary, because the Dem primary is a foregone conclusion for Brandon.
Other states, including NY, are closed primary states where they have voters register by party. Then on primary election day you can only vote in the primary if you registered with that party in advance.