Control of the Pennsylvania House of Representatives hangs in the balance in a special election on Tuesday in the Philadelphia suburbs. If that sounds vaguely familiar, it’s because this is the fourth time in a year the balance of power in the narrowly divided lower chamber has been upended by a vacancy, with a fifth time potentially in the works.

Voters in the 140th state House district in Bucks County, sandwiched between Philadelphia and New Jersey, will pick a replacement for former Democratic state Rep. John Galloway, who was elected to a judgeship last year. Galloway’s departure in December deadlocked the chamber at 101-101, but a new resignation Friday by a GOP lawmaker gives Democrats a 101-100 advantage. Tuesday’s primary will either slightly strengthen a Democratic majority or return the chamber to a tie.

Read more at AP.com.