PITTSBURGH — Bernie Sanders looked Thursday to extend his recent winning streak by making inroads in Pennsylvania, a Hillary Clinton stronghold.

Greeted by Pittsburgh-flavored "Here we go, Bernie, here we go" chants, Sanders staked his claim to the union vote as he addressed 8,500 at the David L. Lawrence Convention Center. Two of his three introductory speakers were union members, one from the United Steelworkers union and the other from the United Electrical Workers union.

"When we talk about the shrinking middle class and poverty, we have to talk about our disastrous trade agreements," Sanders told reporters prior to his event. "Trade policy cannot be a policy in which American workers are forced to compete with people making pennies an hour."

During his speech to the packed crowd, Sanders rattled off a laundry list of examples where companies throughout western and central Pennsylvania have shipped jobs overseas, citing "disastrous trade policies" which he rails against regularly.

"On and on it goes," Sanders lamented before hitting Clinton on the issue. "I have opposed from day one in Congress every one one of these disastrous trade agreements. Secretary Clinton has supported virtually every one of these disastrous trade policies."

One of Sanders' highest profile backers in the Keystone State, Braddock Mayor John Fetterman, talked up the Vermont socialist's chances in the state despite polls showing Clinton with a convincing lead. Fetterman, who's one of four Democrats vying to take on Republican Sen. Pat Toomey in November, conceded that while Pennsylvania will not be an easy contest for Sanders, support from union households and minority groups will be crucial.

"Big union turnout, big urban turnout, youth turnout," said Fetterman on Sanders' keys to a strong showing. "I think he's going to perform well with minorities as well, despite the narrative that's out there. I just think he's going to pull strong because his message resonates real deeply with so many communities across the state."

"I know their state director was the same guy that helped him carry Michigan, and the demographics are very similar here — Rust Belt states," Fetterman continued. "I'm not making any odds or wagers on that, but it's going to be close and it's going to be competitive."

Union support will be crucial, specifically in areas like Pittsburgh and western Pennsylvania overall. In 2008, Clinton topped Barack Obama in western Pennsylvania and with strong support from union households to counteract the Philadelphia minority vote for Obama. Union members were out in droves for Sanders Thursday.

"You see these hands?" Tom Keene, a 67-year-old former union member, said rhetorically when asked why he supports Sanders. "These hands were crippled with carpeltunnel so bad."

"But my hands are rebuilt, and you know how they got rebuilt? That man, right up there," Keene, a Greene County resident, said pointing to Sanders. "He put money in the [Veterans Administration] so that I could get my hands back. That's why I'm here. He supported me, took me off the streets. I was homeless. Now I have some place to live, and I have my hands back."

Currently, Sanders trails Clinton among Pennsylvania Democrats, with 53 percent backing the former secretary of state to only 28 percent for Sanders, according to the latest Franklin & Marshall poll. In addition to winning there in 2008, Bill Clinton carried the state in 1992 and 1996.

Sanders' campaign stop in Pennsylvania is also the first of any candidate since the start of the year on either side of the aisle, though candidates are likely to descend on the state after the Wisconsin primary. It's one of one of four Mid-Atlantic states with contests looming, with contests in New York (April 19), Maryland and Delaware (both April 26) all on the docket.

Sanders' Pittsburgh campaign swing was one of two stops of the day, with the second set for 7 p.m. in Bronx, N.Y.