(CNN) At the United Steelworkers rally for Conor Lamb, there are three union steelworkers supporting the Democrat in his bid against Republican Rick Saccone for a house seat in the special election in Pennsylvania 18th District.

The trio are registered Democrats. Two voted for Hillary Clinton in the 2016 election. One, Edward Yorke, did not.

"I voted for Trump" Yorke, 63, said.

"I feel the President is doing a fantastic job under the circumstances," Yorke added. "It's about time, we had to do something about the tariffs."

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. But now, with polls suggesting a close race, the district's special election on Tuesday will be a test of Trump's popularity heading into the midterm elections and whether Democrats can compete in Trump country. Lamb must win over some of Trump's voters to succeed Tuesday.

Trump won in this district in part because of his tough talk on trade. The 18th is the heart of steel country where nearly everyone knows someone who worked in the industry.

His recent move imposing a 25% tariff on steel imports and a 10% tariff on aluminum import is popular in the district: Saccone and Lamb have both expressed support for the tariffs and the United Steelworkers Union, which represents nearly 18,000 union members in the district is also on board.

But it doesn't appear from speaking with union leaders and members here that Trump's popular move will necessarily translate to increased support for his chosen candidate, Saccone.

"Conor Lamb would give me his ear," Yorke. said "As far as Saccone, I don't feel comfortable and I would tell the President that also: 'Sorry, I wish I could help you out, but Saccone doesn't impress me at all.'"

Tim Waters, the political director for the United Steelworkers Union, "We applaud the President for what he did and for drawing a line in the sand. It's what he said he was going to do and it needs to be done. This is not a political issue."

The steelworkers union has been joined by members from the teachers, hotel, and postal workers unions in getting out the vote for Lamb. Together they have 80,000 union members in the 18th District, which translates to that many potential voters.

For the past few months, members have been canvassing neighborhoods in the district -- sometimes four or five times -- and knocking doors of other members. Denny Cregut is a former steelworker who now works for the United Steelworkers Union. He and his wife Kelly spent the weekend before the election visiting dozens of households to remind people to vote. In an hour, just two people came to answer the door.

Waters believes direct voter contact is a winning strategy. Soon after Lamb announced his candidacy, he met with labor unions and visited local steel mills and processing facilities. Lamb opposes so-called "right-to-work" laws, which prevent unions from mandating dues payments from members they represent.

Saccone told reporters Saturday that the "right-to-work thing is always a tricky thing" but that it wouldn't be a problem for unions if they were willing to compete.

"Rick Saccone was endorsed wholeheartedly by the right-to-work committee and would probably do away with unions if he could," Waters said.

Jason White, who spent two years working in the coal mining industry and was a part of the United Mine Workers of America, which also endorsed Lamb, sees it differently.

White was a Democrat until 2012 when he switched parties, and now he's supporting Saccone.

"I've never heard Rick say he's against unions," White said. "I think he is just pro giving someone a choice."

He doesn't think union leadership has the backing of its members like it used to.

"I think they're breaking with leadership," White said. "If you talk to anybody on the side, and go behind closed doors and have discussions, you get a pretty good gist of how people feel."

That could prove tricky for the union who are hoping their members turn out in high numbers. The union hopes their members will make up 30% of the electorate on Tuesday.

"I think what we've seen in the recent years that the endorsement from union leadership doesn't carry as much weight as it used to," said Chris Bonneau, a political scientist from the University of Pittsburgh. "I don't think it's a conscious breaking from the leadership just so much as the leadership doesn't have as much of sway or sway over its members."

Someone who still has sway in southwest Pennsylvania -- Donald Trump. He drew a packed crowd to his rally with Saccone on Saturday, with some supporters having to be turned away.

"I think people appreciate what he's done," said White. "And you have Rick Saccone, who supports that agenda. So to go against the party lines and go against that agenda doesn't make a whole lot of sense. And this tariff is kind of an exclamation point for how people feel."