There exists a vacancy in the 18th Congressional district of Pennsylvania (Mount Lebanon and Greensburg), vice Timothy Francis Murphy, resigned.
The Eighteenth District is seen as a probable Republican hold. It re-elected Murphy without opposition in 2016; in 2012, Murphy was re-elected with 64% of the vote. The district gave Donald Trump a 58.1%-35.1% margin in 2016 and Mitt Romney a 57.9%-41.0% margin in 2012. This area last sent a Democrat (Frank Mascara) to Congress in 2000, prior to the 2002 redistricting that made the seat significantly more Republican and elected Murphy.
The partisan composition of the House of Representatives is now 239 Republicans and 194 Democrats, with two vacancies. A date for the special election has not yet been set.