Almost everyone - Democrat, Republican, independent - said the tariffs announcement had no effect on how they planned to vote. The average of polls taken since February 12th suggests that Mr Lamb is running two percentage points behind Mr Saccone.
He has eschewed the national Democratic brand, saying he would not support House Democratic leader Nancy Pelosi as speaker.
Lamb, however, keeps to party orthodoxy on unions.
A lackluster performance, on the other hand, could reveal the limits of Moulton's ability to sway voters in conservative districts and tap into anti-Trump energy.
"The basic conversation on campus is pretty split, for the most part", Markish said. "It's a good gamble".
Win or lose tomorrow, Lamb could run in November in a reconfigured district, numbered the 17th, where Rep. Keith Rothfus (R) is expected to seek re-election.
Outside money has played less of a role on Lamb's behalf. "I just don't understand that people say we shouldn't put lobsters into hot, boiling water. but we can kill babies".
While Trump was ostensibly in Pennsylvania for Saccone, the rally was as much about the president as it was an underperforming congressional candidate.
"You'd be so bored", Trump said as he brushed off criticism that he should change his ways.
Pennsylvania voter Michelle Grimpe similarly tells CNN that she's backing Saccone - but she says that she doesn't "like necessary how the president presents himself" and she said that Trump's attitude made her feel tempted to back Saccone's rival, Democrat Conor Lamb.
The Emerson poll results are within the margin of error of 4.8 percentage points and until recently polls unanimously predicted at least a narrow victory for Mr Saccone.
But while both sides have decided that the race is worth digging deep into their pocketbooks, the fact remains that, unlike Virginia and part of Georgia where candidates also went head to head previous year, this area in Pennsylvania voted solidly and overwhelmingly Republican in 2016.
"This is the kind of election where even turning out an extra 2,000 voters who are young could actually make a difference", Ginsberg said. And it's an unsustainable spending rate if similar Republican-heavy districts become competitive in the November midterm elections. "It's clear people want an alternative to Trump". In 24 consecutive special House elections, the party defending the vacant district has been victorious, according to data compiled by Bloomberg Government.
Donald Trump Jr.is coming to Pittsburgh Monday to stump for Saccone ahead of Tuesday's special election.
Donald Trump won the 18th Congressional District by 20 points against Hillary Clinton in the last presidential election.
The special election has been treated in the media as a referendum on Trumpism: these voters, according to the narrative, are the disenchanted Democrats who spurned their party for Trump in 2016.
Lamb has vowed not to vote to back Pelosi if he is elected to Congress and has taken several other moderate positions.
This is a total reversal of Monmouth's poll last month.
For his part, Saccone was thrilled to have the president's help.
"The world is watching", Trump said in an appearance in the district Saturday night, upping the pressure for Saccone to deliver on Tuesday.
The longer-term prize is the House of Representatives. After prosecuting military cases in Okinawa, Japan, he returned home to serve as an Assistant U.S. Attorney, devoting much of his efforts to tackling illegal drugs, particularly opioids. But Lamb did get help from former Vice President Joe Biden, a favorite among Rust Belt Democrats. "So I don't think it's a responsible thing to do".
If he loses, it could foreshadow what is already expected to be a hard midterm election cycle for Republicans.
TRUMP: Regulation, tax cuts, federal judges, a great, great Supreme Court.
Instead, Saccone has been boosted by more than $10.6 million support from super PACs and outside groups, including $3.4 million from Congressional Leadership Fund, $3.5 million from the NRCC and $1.1 million from America First Action.
Ingeborg Moran, 27, is also supporting Lamb. "He's progun, he's protariff, he's pro-Trump essentially, " she said. Democratic groups spent only $855,591.