Why does Pennsylvania require political party affiliation to vote in the primary?

Pennsylvania requires voters to declare a political party affiliation to participate in primary elections to ensure that only registered party members can vote on their party's candidates. This system helps maintain the integrity and organization of the primary process, allowing parties to select their nominees based on the preferences of their own members. It also encourages party loyalty and engagement among voters, as they actively participate in shaping the candidates who will represent their party in the general election.