By Eric Bradner, CNN

(CNN) -- Joe Biden began his first rally as a 2020 presidential candidate arguing that President Donald Trump had abandoned voters in white, working-class America -- and that reconnecting with those voters is Democrats' path to victory.

The former vice president told the crowd he decided to hold his first campaign rally in western Pennsylvania because, for the Democratic Party, it is among the "places where lately we've had a little bit of a struggle."

"If I'm going to be able to beat Donald Trump in 2020, it's going to happen here," he told the crowd.

The 76-year-old Biden launched his campaign last week with a much more direct focus on Trump than other Democratic presidential contenders. On Monday, he said -- in a twist on former President Barack Obama's 2008 campaign theme -- that Americans must "choose hope over fear, unity over division and, maybe most importantly, truth over lies."

"Donald Trump is the only president who has decided not to represent the whole country. The President has his base," Biden said.

Trump rode a wave of white voters in swing states -- particularly Pennsylvania, Michigan and Wisconsin -- fleeing Biden's party. Biden's campaign is based on the premise that he's the candidate best able to connect with voters in those areas -- and his rhetoric on Monday was a direct appeal to them.

"I make no apologies: I am a union man," he told the largely white crowd at a Teamsters union hall.

A Biden ally was even more blunt about his appeal. Minutes before the former vice president took the stage, International Association of Firefighters president Harold Schaitberger -- whose union endorsed Biden earlier Monday -- told the crowd that Democrats "can't have a nominee that's too far left."

He warned of candidates with "high-minded ideals, maybe honorable ideals, but little chance of winning. And there's no question that the candidate who can win -- the candidate who will be our next president -- is Joe Biden."

And he took a shot at the 2016 Democratic presidential nominee, Hillary Clinton, saying that Democrats need a 2020 candidate who "connects with those workers who don't believe the last Democratic nominee listened to them or cared about them."

Biden didn't get into the specifics of policy in his first rally as a presidential candidate, but he did lay out the beginnings of a platform for his campaign. Among the policies Biden touted: a "public option" that would allow anyone to buy into Medicare; a $15-an-hour minimum wage; eliminating capital gains tax loopholes; and increasing funding for medical research and post-secondary job training.

Biden also repeatedly said he would undo Trump's tax cuts, complaining that the benefits had accumulated with wealthy Americans and corporations.

"Did you feel it? Did you get anything from it?" he asked the crowd while bashing Trump's tax cuts, eliciting a round of "no" responses. "Of course not! Look, guys, this is not good."

Biden argued that the nation's premise of the middle class was being undercut by a "one-way street" greedy companies with executives who pump money into salary increases and stock buy-backs rather than worker pay.

"We have to rethink how we define what constitutes a successful economy. It's not enough for the stock market to rise. That's not a bad thing, but it's just not enough. Workers feel powerless, too often humiliated," Biden said. "We're tearing America apart instead of lifting it up."

Earlier on Monday, Trump -- provoked by Biden's comments about white supremacist violence at Charlottesville, Virginia, and Biden receiving the endorsement of the International Association of Fire Fighters union -- directed his ire at Biden.

"The Media (Fake News) is pushing Sleepy Joe hard. Funny, I'm only here because of Biden & Obama. They didn't do the job and now you have Trump, who is getting it done - big time!" Trump tweeted Monday morning.

He also complained about Biden receiving the firefighters' union's endorsement.

"I'll never get the support of Dues Crazy union leadership, those people who rip-off their membership with ridiculously high dues, medical and other expenses while being paid a fortune. But the members love Trump. They look at our record economy, tax & reg cuts, military etc. WIN!" Trump tweeted.

Twenty-three minutes later, after another tweet about "Sleepy Joe Biden" rallying in Pittsburgh, Trump added: "The Dues Sucking firefighters leadership will always support Democrats, even though the membership wants me. Some things never change!"

Before his rally Monday afternoon, Biden responded on Twitter.

"I'm sick of this President badmouthing unions," he said. "Labor built the middle class in this country. Minimum wage, overtime pay, the 40-hour week: they exist for all of us because unions fought for those rights. We need a President who honors them and their work."

The fight goes to the heart of Biden's case for the Democratic nomination: He aims to build on former president Barack Obama's coalition by appealing to white working-class voters in states where Democrats saw their support slip away during Obama's tenure in office. Though the dynamics of the electoral map can always shift, Democrats could win back the presidency by holding onto the states Hillary Clinton won and rebuilding their "blue wall" in Pennsylvania, Michigan and Wisconsin.

Biden's first week on the campaign trail will also include a two-day swing through Iowa, with events planned for Tuesday in the eastern part of the state and Wednesday in central Iowa.