Pennsylvanians have until the close of business Monday to register if they want to vote in the May 15 primary, but they can sign up online.
Voters must be registered with the Democratic or Republican parties if they want to cast ballots to help pick the major parties' nominees.
This year's elections include governor, U.S. senator, Congress, half the state Senate and all 203 state House seats.
There are also special elections to fill vacancies in the state House created by the departures of former state representatives Matt Baker of Bradford County, Brandon Neuman of Washington County and Scott Petri of Bucks County.