WASHINGTON — Former Vice President Joe Biden will launch his long-awaited campaign for president with a video release Thursday, and will visit a union hall in Pittsburgh on Monday, according to a source with direct knowledge of his plans.

The source confirmed reports from NBC News and others detailing the rollout for Biden, who will enter the Democratic primary as the leader in public polling.

Biden, 76, will join a crowded Democratic field as an elder statesman, known for his eight years as vice president to Barack Obama, for decades as a Delaware senator, and for his blue-collar persona, built off of his roots in Scranton.

Yet Biden also will face a changing Democratic Party, one in which some activists are seeking younger voices who reflect the party’s diverse coalition, which depends increasingly on women and people of color. His more moderate stances could be out of step with a vocal faction of the Democratic electorate.

But Biden allies, including a significant portion of the political establishment in Pennsylvania, see him as the party’s best chance to win back moderate swing voters and defeat President Donald Trump.

A group of Philadelphia-based Democratic insiders with long ties to Obama and Hillary Clinton are planning a Thursday fund-raiser hosted by Comcast senior executive vice president David L. Cohen to try to give Biden a boost as he tries to catch up to other Democrats who have been raising money for months.

Former Gov. Ed Rendell, a member of the host committee for the event, said Tuesday the response has been “overwhelmingly favorable,” noting that Biden was often referred to as Pennsylvania’s third senator during his time serving in the U.S. Senate from Delaware.

Fund-raiser tickets are $2,800 per person, the federal maximum for individual donations. Rendell said Cohen’s house, which has hosted fund-raisers for Obama and Clinton, can hold about 200 people if a tent is erected there and about 125 if not.

“He’s definitely running,” Rendell said. “He feels good about it. He thinks it’s right for the country.”

This would make Biden the 21st Democrat in the 2020 field. Rendell isn't worried about the crowd.

“I think when you look at the field, his experience and preparation for being president stand out markedly,” Rendell said. “He’s just got an extraordinary length and breadth of service.”

Rendell said the only public event for Biden in Philadelphia so far is a rally tentatively scheduled for mid-June.

Biden had tentatively planned to begin his run Wednesday, and had considered initial events in Charlottesville, Va., and Philadelphia. Democratic sources close to his campaign expected events in those cities last week, but those plans were never finalized. As recently as Monday, his supporters in Philadelphia were unclear whether the fund-raiser would be able to go forward, but they appeared to have assurances Tuesday.