Seven of these 18 seats are vacant, due largely to the departures of 5 Republican lawmakers who both have resigned or are usually not operating once more.
The Pennsylvania Supreme Court added another wrinkle to the race in February, when it redrew the district boundaries in a way many observers considered favorable to Democrats.
He paid little attention to his Republican rival during the primary campaign. No fewer than ten Democrats had been operating in suburban Philadelphia's fifth District, the place Rep. Patrick Meehan resigned final month amid allegations he sexually harassed a former worker.
Within the southwest nook of the state, the brand new 14th District provided an opportunity at redemption for state Rep. Rick Saccone.
The president used Twitter to urge Nebraska Republicans to "make sure you get out to the polls and VOTE" for Sen. He's running against Guy Reschenthaler for the GOP nomination in the deep-red western Pennsylvania district.
Voters also will pick candidates for the November ballot for the full U.S. House and the full state House and half the state Senate. Others have criticized Reddick for being a registered Republican until 2016.
Barletta has lagged in the fundraising race, collecting almost $1.3 million in 2018's first quarter and ending with $1.6 million on hand, compared to Casey's almost $10 million on hand. He's backed by a group with ties to the centrist "No Labels" group, but is a target of progressives over his stances on abortion, illegal immigration and a series of now-deleted tweets that included praise for President Donald Trump.
The victor of the three-cornered fight between Wallace, Reddick and Steve Bacher likely will face Republican incumbent Brian Fitzpatrick in November.
The race for one of Pennsylvania's two U.S. Senate seats will feature incumbent Democrat Bob Casey going up against Republican Lou Barletta in November's general election. The victor will advance to a showdown against two-term Democratic Sen.
Barletta, who has 60 percent of the vote with 52 percent of the precincts reporting, will face incumbent Democrat Bob Casey in the November general election.
"Trump has not been particularly successful in translating his own popularity with his base to voters from that base for other candidates", said University of Pittsburgh political scientist Kristin Kanthak.
Barletta was an early Trump supporter, and the president encouraged him to run for Senate.
Republicans have already privately anxious that the divisive Barletta, like Trump an immigration hardliner, could hurt the rest of the GOP ticket in a state where more than a half-dozen House seats are up for grabs this cycle, a lot of them Democratic pickup opportunities.