"The people of Pittsburgh cannot be conned by this guy Lamb," Trump said, dismissing Lamb's efforts to run as a moderate Democrat.
"He's never going to vote for us. He can say, 'I love President Trump.' ... I don't want to meet him. I might like him."
Democrats need to flip 24 GOP-held seats to claim a House majority. A victory in such a Republican-leaning district would boost their hopes and renew GOP concerns of a bad November.
Lamb, a 33-year-old Marine veteran and former prosecutor, has positioned himself as more representative of the district than Saccone, a 60-year-old state lawmaker.
Lamb touts his resume and declares that he wouldn't vote for Democratic House leader Nancy Pelosi as party leader. He also avoids criticizing Trump.Trump conceded Lamb might not back Pelosi but said most House Democrats will. And if Pelosi were in charge of the House, Trump said, Lamb would simply "vote the party line."
While Trump was ostensibly in Pennsylvania for Saccone, the rally was as much about the president as it was an underperforming congressional candidate.
The president repeatedly reminisced about his election, when Pennsylvania helped put him over the top after decades of landing in the Democrats' column.
The president criticized Democrats for blocking his long-promised border wall and attacked so-called sanctuary cities that refuse to cooperate with federal immigration authorities.
He also called for harsher punishments for drug dealers, including the death penalty, pointing to China and Singapore as modelsTrump continued his attacks on the press, criticizing media coverage of his decision to meet with the leader of North Korea and complaining that he doesn't get credit for accomplishments.
He singled out NBC's Chuck Todd as a "sleeping son of a bitch."
He also made sure the workers in this industrial-heavy region see the new steel tariffs as "my baby," even as Lamb and Saccone have endorsed the move.
Pennsylvania's 18th Congressional District has an estimated 17,000 steelworkers and almost 90,000 voters from union households.
"Not all of our friends on Wall Street love it, but we love it," Trump said of the tariffs. He added that Lamb's party leadership opposes his protectionist policy.
He sidestepped the fact that most of his own party's leaders oppose tariffs, as well.
Trump's appearance was part of a White House push to help Saccone avoid a once-unlikely defeat. National GOP forces could exceed $10 million in spending on the race, and Saturday was the president's second recent visit to the area.
But Trump risked another embarrassing defeat after backing Republican Roy Moore in last December's Alabama Senate election, only to watch Moore lose a seat his party had held since 1997.The Pennsylvania special election is to replace Republican Rep.
Tim Murphy, who resigned last year amid revelations of an extramarital affair in which the anti-abortion lawmaker urged his mistress to get an abortion when he thought she was pregnant.
Murphy, an eight-term congressman who had union support, never had a close election and had no Democratic challenger in his last two elections.
But Saccone has struggled with his own fundraising, is a union foe and hasn't run as aggressive a campaign as Lamb, prompting criticism from Republicans in Washington who quietly concede Lamb is a stronger candidate.
Trump acknowledged those dynamics, noting talk of Lamb as a handsome candidate.
But he said he thinks he's better looking, and added that Saccone "is handsome," too.
For his part, Saccone was thrilled to have the president's help.
"The president's support is key to attaining victory," Saccone told rally attendees about 45 minutes before Trump took the stage.
"There's no one that I would rather have in my corner that President Trump. Are you with me on that?"
-AP
