Registration and mail ballot deadlines are hard cut-offs, and Pennsylvania counts mail ballots by when they arrive rather than when they were posted. Every date below is transcribed from the Department of State calendar.
In a Pennsylvania primary you may only vote for candidates of the party you are registered with. Independent and third-party voters can still vote on ballot questions and special elections, but not in a major party's primary contest. Changing party affiliation requires updating your registration before the registration deadline — not on primary day.
Source: Pennsylvania Department of State — Upcoming Elections ↗ — retrieved July 25, 2026. Dates can shift by court order or legislation; confirm with the Department of State or the Board of Elections before relying on any deadline.