Pennsylvania‘s primary has set the table politically for a knife-fight fall campaign — and the winners could determine whether Democrats take back control of the House of Representatives.

Four Republican-held congressional districts are at the center of it: the Bucks County-centric 1st held by Rep. Brian Fitzpatrick (R-PA); the Lehigh Valley-based 7th held by Rep. Ryan Mackenzie (R-PA); the 8th, covering Scranton, Wilkes-Barre, and northeastern Pennsylvania represented by Rep. Rob Bresnahan (R-PA); and the 10th covering the Harrisburg and York areas held by Rep. Scott Perry (R-PA).