Karloski, a steelworker and registered Democrat, voted for Republican Donald Trump as someone who appealed to his middle-class sensibilities, although he had no real love for a presidential candidate he saw as the "lesser of two evils."
Karloski was looking for new and different people to change the tone in Washington. He is in the middle politically on debates over abortion and gun rights. As a steelworker, Trump's steel tariffs are important to him and, as a union member, union rights are important.
For Karloski, Lamb's positions fit his on all those issues; Saccone's fit almost none.
"It's time to get a younger person in there, somebody who will work with both sides of the aisle and not just be a backstop for Trump," Karloski, 53, said after voting in this Pittsburgh suburb.
Karloski's vote showed how Democrats tolerated Lamb's centrist stances on certain hot-button issues, as well as his move to downplay Trump's role in the race, while liberals, labor unions and even Democrats who supported Trump rallied around Lamb's embrace of core party positions on issues such as Social Security and health care.
Lamb, a 33-year-old former federal prosecutor and first-time candidate, held a roughly 600-vote lead out of more than 228,000 cast in a nationally watched election over Saccone, 60, a four-term state lawmaker who ran as Trump's "wingman" after compiling one of the most conservative voting records in Pennsylvania's Legislature.
The Associated Press has not called the race. Lamb has declared victory while Saccone's campaign has said he has no plans to concede before the counting of a few hundred remaining ballots wraps up Tuesday.
Several months ago, few thought it possible that a Democrat could win this district. Trump thrashed Democrat Hillary Clinton there by nearly 20 percentage points in 2016's presidential election. Former Rep. Tim Murphy, a pro-union Republican who resigned in a scandal in October, had been re-elected there seven times, always easily, in a district Republicans drew for him.
On paper, the district might appear Democratic: it has more registered Democrats than Republicans. That's a relic of union families tied to the district's long history of coal mining and steel-making. But southwestern Pennsylvania began sending Republicans to the state Capitol and Washington in the past decade or so as blue-collar whites fled the Democratic Party.
In Tuesday's election, it seemed more like a Democratic district again.
Democratic energy was high: Lamb won 47 of the 50 precincts with the highest percentage turnout in Allegheny County, the district's most-populous county, according to an Associated Press analysis of the results. In 2016, Trump won 30 of the 50 highest-turnout precincts in the county.
First-time activists fueled by an anti-Trump fervor worked on Lamb's campaign, knocked on doors for volunteer groups or started a local Democratic Party committee in their neighborhood.
Democrats seemed unbothered by Lamb's drift from liberal orthodoxy on the hot-button issue of guns, such as his opposition to an assault weapons ban.
Republicans even tried to peel away liberal voters on that issue, with a super PAC allied with Republican House Speaker Paul Ryan - the Congressional Leadership Fund - sending mailers to registered Democrats highlighting Lamb's opposition to more sweeping forms of gun control.
For Carol Marraccini, a retired commercial real estate broker and registered Democrat, gun control is her top issue. She is frightened by gun violence in schools and still voted for Lamb, hoping he will advance a gun-control agenda in Congress.
"I hope that his position will change," Marraccini said.
It was clear that Democrats nominated a strong candidate: voters liked Lamb's youth and looks, often calling him "fresh-faced" or "refreshing." Even Republicans admitted that Lamb's youth was an asset. Brian Konick, a registered Democrat who voted for Trump in 2016, voted for Lamb on Tuesday, liking his "newer thought, newer blood."
Libertarian Drew Miller drew about 1,400 votes, or roughly twice Lamb's lead over Saccone.
But Saccone was gravely damaged by his support for anti-union legislation. Murphy, who resigned amid a sex scandal in October, had long supported union-backed legislation, and unions supported him.
Labor support for Lamb was so unified that the United Mine Workers endorsed him after it sat out the 2016 election rather than back Clinton.
At a rally last Sunday, Cecil Roberts, the mine workers' president, delivered a rousing, sermon-like endorsement of Lamb and summed him up as he sought to sell him to the crowd: "He's a God-fearing, union-supporting, gun-owning, job-protecting, pension-defending, Social Security-believing, health care-creating and sending-drug-dealers-to-jail Democrat!"
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