Democrats appear to be in position to flip at least three, and perhaps as many as six, of Pennsylvania’s 18 House seats, according to strategists from both parties. That could represent a quarter of the 24-seat gain they need nationwide to take control of the House.

“Pennsylvania will be the epicenter of the political world this fall,” said Charlie Gerow, a Republican strategist in the state. With so many seats in play, he predicted that “gobs of money” would flow in.

The prospect has caused a geyser of candidates: As of Tuesday, 58 Democrats and 35 Republicans were seeking House seats, according to the Department of State.

Behind the altered political terrain are two restive groups of voters.