But Mr Lamb's surprisingperformance - polls show him tied or within the margin of error against Mr Saccone - has boiled down to Mr Trump's polarising presidency, said Democratic Congressman Michael Doyle. These were the focus of Vice President Mike Pence when he went up to campaign for Saccone, barely mentioning stress points like trade or immigration. See?
The district's previous congressman, Republican Tim Murphy, resigned a year ago amid an adultery scandal.
Lamb is "a very attractive candidate, and the optics of comparison between them have not been favorable to Saccone", Harold said.
Voters like Yorke, who are registered Democrats and have supported Democrats in the past, gave Trump a victory by 20 points in the 18th District.
By contrast, the Democratic Congressional Campaign Committee only spent $312,500 to back Lamb. "We need more people like that in Congress on both sides of the aisle".
Over the weekend, Lamb celebrated an endorsement from the United Mine Workers, a union that sat out the 2016 election rather than endorse Trump or Hillary Clinton. As a former federal prosecutor, he led aggressive prosecutions against drug dealers, which makes him popular in communities in western Pennsylvania hit especially hard by the opioid epidemic.
"In other words, districts that Trump won convincingly", he said.
He says Democrats are "throwing everything they can at this race" because it's a rare open seat.
That apparently includes Scott von Wertmann's neighbour in the township of Upper St. Clair, an affluent suburb south of Pittsburgh in Allegheny County. Murphy resigned in October amid a sex scandal.
GOP and Trump-aligned groups have spent more than $10 million to prop up Saccone.
The Pennsylvania Supreme Court, after ruling that the map drawn by the Republican-controlled legislature amounted to unconstitutional gerrymandering, ordered new districts for the November election. The AFL-CIO estimates there are 87,000 votes from union households in Pennsylvania's 18th district, around a fifth of the electorate. In a more-restrictive turnout model - created to mirror a lower-turnout electorate that typically votes in midterm elections - Lamb has a slim, 2-point lead, 49 percent to 47 percent. The tariffs on steel and aluminum Trump has announced are tailor-made for blue-collar neighborhoods outside Pittsburgh, though the once-fabled "Steel City" has diversified its economy around sectors such as technology and health care in the 21st century.
It's no secret that many establishment Republicans (and even non-establishment Republicans) hate and fear Donald Trump. Former Vice President Joseph Biden's visit to the district last week to campaign for Democrat Conor Lamb was an example of how these typically go: Biden appealed to voters to choose Lamb, going so far as to compare the candidate to his own deceased son, former Delaware Attorney General Beau Biden. He rambled for over an hour about a wide variety of topics that didn't do anything to help Rick Saccone.
Pennsylvania politicos, meanwhile, are baffled by the Republicans' decision to put Saccone on the ballot. If there's a surge of Democratic support for Lamb, however, the poll had him up by six points, 51-46 percent. "I do not believe, as (Republican House Speaker) Paul Ryan does, that these are entitlements or another form of welfare".
Labor is looking to Lamb to score big with that group and offer the movement signs of a comeback that could sway key Senate and governor's races this fall.
Lamb has raised almost $4 million dollars; Saccone can boast just one-fifth of that, and has relied heavily on Republican outside groups to bankroll much of his campaign. On the stump he sounds more like a Republican than a Democrat, and he vows to be an independent willing to make life miserable for Nancy Pelosi and the dominant Democratic left in the House. It would follow Democratic victories previous year in a special Senate election in solidly Republican Alabama, as well as wins in Virginia, New Jersey and a handful of state races in other parts of the country.
What time do polls close?
At a rally for Saccone on Saturday night in the heart of the district, which stretches from the suburbs of Pittsburgh to the border with West Virginia, Trump laid out the stakes in Tuesday's vote.