Former Vice President Joe Biden Joe BidenBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Democratic groups using Bloomberg money to launch M in Spanish language ads in Florida Harris faces pivotal moment with Supreme Court battle MORE is touting a theme of unity and pushing back on those who may urge Democratic presidential candidates to be "angry" in their bids to take on President Trump Donald John TrumpBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power Two Louisville police officers shot amid Breonna Taylor grand jury protests MORE.

Biden is set to hold a campaign event Saturday in Philadelphia to officially kick off his White House bid, casting himself as a unifier in a crucial swing state that split its popular vote nearly evenly between Trump and Hillary Clinton Hillary Diane Rodham ClintonDemocratic groups using Bloomberg money to launch M in Spanish language ads in Florida The Hill's Campaign Report: Presidential polls tighten weeks out from Election Day More than 50 Latino faith leaders endorse Biden MORE in 2016.

“Some say Democrats don’t want to hear about unity. That they are angry – and the angrier you are – the better. That’s what they are saying [you] have to do to win the Democratic nomination," Biden will say, according to excerpts circulated by his campaign.

"Well, I don’t believe it. I believe Democrats want to unify this nation. That’s what we’ve always been about. Unity,” Biden is expected to say.

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While putting the emphasis on unity, Biden is also keeping up the pressure on Trump, bashing him as a ruler with a “hard heart.”

“If the American people want a president to add to our division, to lead with a clenched fist, closed hand and a hard heart, to demonize the opponents and spew hatred – they don’t need me. The already have a president who does just that,” Biden will say.

“I am running to offer our country – Democrats, Republicans and Independents – a different path.”

Biden has quickly emerged as the front-runner in the crowded Democratic presidential field, topping every national poll since he announced his White House bid last month and hauling in millions of dollars in donations.

However, he remains dogged by criticism from some on the left over issues such as criminal justice reform and his handling of sexual harassment, with many from the party's progressive flank questioning whether he is the right candidate to lead an increasingly diverse and liberal party.

The former vice president appears set to angle his campaign’s appeal to white working-class voters who traditionally voted Democrat but supported Trump in 2016, a message aimed at winning back Rust Belt states such as Pennsylvania, Michigan and Wisconsin.

Biden, a Scranton, Pa., native, is also basing his campaign in Philadelphia. He has repeatedly played up his Pennsylvania roots and "Middle-Class Joe" nickname to suggest he understands the struggles of America’s blue-collar workers.