Pennsylvania will fill the empty seat of resigned U.S. Rep. Patrick Meehan in a special election on Nov. 6, the day of the general election.
Wednesday's announcement by Gov. Tom Wolf also will apply to the expected resignation of U.S. Rep. Charlie Dent.
That would leave a special election winner just two months in office before a successor picked in the general election takes over for a full two-year term in Congress.
Meehan and Dent, both Republicans, were facing a hostile electorate in 2018 in increasingly liberal eastern Pennsylvania districts.
Meehan resigned abruptly on Friday, three months after it emerged that he had used taxpayer money to settle a former aide's sexual harassment charges.
Dent said last year that he wouldn't run for another term, and last month said he'd resign sometime in May.