Philadelphia, Pa – The "single most important thing we have to accomplish is defeat Donald Trump," former Vice President Joe Biden said Saturday at his presidential campaign's "official" kickoff rally in Philadelphia. Biden also called for "unity" across the country.

Now in his third bid to join the elite presidential club, Biden spoke on a boulevard draped with flags of foreign countries while facing a tall statue of the country's first president, George Washington.

In the "birthplace" of American democracy, Biden leveraged criticism this week of his reported climate change proposal and said the "first and more important plan" in his forthcoming policy rollout will be to "beat Trump, beat Trump, beat Trump."

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"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. They already have a president who does just that," Biden told the crowd, "I am running to offer our country — Democrats, Republicans and Independents — a different path."

"They say Democrats are so angry, that the angrier a candidate can be, the better chance he or she gets the Democratic nomination," Biden argued. "Well, I don't believe it… I believe Democrats want to unify this nation. That's what our party's always been about."

Even if Democrats do not want an "angry" candidate, many told CBS News that they want a "fighter."

Attendees noticed during the speech that Biden faced the nearby stairs Sylvester Stallone famously climbed during his 1976 boxing mega-hit "Rocky," where the fictional American boxer's fight-to-the-end spirit was symbolic, intentional or not, of Biden's efforts to combat criticisms of old age and previous policies for which Democrats try to knock him.

"He is as sharp as a tack," Debra Buzio, 61, said of the 76-year-old Biden, "We need a world leader right now."

Marie Wilson, 65, said that criticisms of Biden's age are moot, as Democrats value the service and intellect of even older public figures like Supreme Court Justice Ruth Bader Ginsburg.

Younger Democrats like Shelby Ferguson, 22, said "values matter" and that Biden would stick up for those norms.

Joe Biden greets supporters at a campaign rally in Philadelphia Saturday, May 18, 2019. Bo Erickson / CBS News

Around 6,000 people attended the rally, according to the private security firm hired by the Biden campaign.

The choice of venue also appeared to reflect the importance of vying for the votes of Pennsylvanians, a state won by President Trump in 2016, though 2018 saw Democratic gains across the state in the congressional contests.

"For both the Democratic and Republican campaigns, Pennsylvania will be crucial," Biden supporter and Democratic Rep. Brendan Boyle, who represents a portion of Philadelphia, told CBS News in an interview. "It will be the most important state it terms of winning the White House so putting an early emphasis on it… shows just how important it is to the Biden candidacy."

Knowing this, Biden, who spent his younger years in Scranton, Pennsylvania, spoke to a crowd of mostly union members at his first rally a little more than three weeks ago in Pittsburgh. "If I'm going to be able to beat Donald Trump in 2020, it's going to happen here," he said then.

The Biden campaign announced their national headquarters in Philadelphia this week, which is dually convenient for the Bidens as their home is a short drive away in Delaware. Their popularity appeared evident before the rally as many locals, politicians like Delaware Democratic Sens. Chris Coons and Tom Carper, several donors and Biden's family gathered at a Philadelphia restaurant, according to several attendees.

Statewide, a Quinnipiac poll this week depicted how this Pennsylvania-centric campaign could ultimately benefit Biden as he bested Mr. Trump by 11 points in a hypothetical match-up race in the state.

But before Biden can compete against Mr. Trump in the 2020 election, he must clench the Democratic nomination — a feat nowhere near locked down as the field of candidates continues to grow.

Sen. Bernie Sanders from Vermont in the Quinnipiac poll also beat Trump in Pennsylvania by seven points and many Democrats throughout the country at Biden's rallies told CBS News they'll support whoever ends up as the nominee.