As a result of the 2018 elections, Pennsylvania's House delegation to the 116th U.S. Congress took office in early January 2019 with a tie of 9 Republicans and 9 Democrats.
Republican Tom Marino, the incumbent representative for Pennsylvania's 12th congressional district, announced his resignation effective January 23, 2019. By state law, Governor Tom Wolf was required to call for a special election at least 60 days after the seat became vacant. Wolf set the election for May 21. Primary elections were not held in the race. Instead, nominees were chosen by each party. Republicans selected their nominee on March 2.
According to the Pennsylvania Democratic Party, Marc Friedenberg, the Democratic nominee for the district in 2018, was the only individual who submitted an application to be the nominee. Therefore, the convention was cancelled, and the party declared Friedenberg the nominee on February 12.