On Monday night in Montoursville, Karen Paris and her husband, Keith, a pastor, drove about an hour from Mansfield, Pa., to hear the president, whom she said they supported “from the first day” and remained fervently behind him.
“He’s doing everything he promised he’d do, and we like it,” Mrs. Paris said. “And we really didn’t like Mrs. Clinton.”
And, as if on cue, when Mr. Trump mentioned Mrs. Clinton, the crowd responded with a now ritual chant of “lock her up.”
The special election was prompted by the unexpected retirement in January of the 12th District’s Republican congressman, Representative Tom Marino, two weeks after he was sworn in for his fifth term. The Republican nominee, Fred Keller, a state legislator, is facing Marc Friedenberg, the Democratic nominee and a professor at Penn State, who lost to Mr. Marino in the November midterm election by 32 points.
But for the most part, the 2018 midterms signified a strong comeback for Democrats in Pennsylvania, with Gov. Tom Wolf and Senator Bob Casey easily winning and carrying counties that Mr. Trump won in 2016. Democrats also won three congressional districts from Republicans.
“The Democrats were more enthusiastic about voting, and, most important, they made big in roads in the Philly suburbs — so essential in statewide elections,” Mr. Madonna said.
Mr. DiGiorgio said he was advising the Trump campaign to have the president hold events in Philadelphia to help expand his support.