In a highly populist speech that could foreshadow the themes he would highlight on the campaign trail, Biden said workers have been "clobbered" in the modern economy.

"It used to be when productivity went up in America, everybody got to share. The people who caused the productivity increase, they got to share. They got a piece of the action," Biden said before leading a march of an expected 60,000 workers through downtown Pittsburgh. "Something is wrong, folks."

The march, organized by the AFL-CIO labor union, comes as Biden is weighing a possible late challenge to Democratic presidential front-runner Hillary Clinton and surging Vermont Sen. Bernie Sanders. Still grieving after the death of his beloved son Beau from brain cancer in May, the Vice President is torn over whether his family can bear the emotional toll of what would be his third presidential campaign.

"If I can reach that conclusion that we can do it in a fashion that would still make it viable, I would not hesitate to do it," Biden said last week at a synagogue in Atlanta.

READ: Biden previews 2016 message while pondering run

Rich Trumka, the President of the AFL-CIO, introduced Biden as a friend, a brother and "a great champion of working men and working women."

Biden had been expected to make a decision by a self-proclaimed end-of-summer deadline, but associates now say an announcement by October 1 is considered more likely.

Clinton still holds a commanding lead in the polls. But as talk of a potential run grows, with Clinton unable to quell a controversy about the private email server she used as secretary of state, Biden is seeing a modest uptick in polling.

In the latest poll of New Hampshire primary voters by NBC/Marist released Sunday, Biden had support from 16 % of Democratic voters. That's half the total of Clinton, who herself trailed front runner Sanders by 9 points. In Iowa, Clinton saw her lead over Sanders decline by half and now leads him by 37% to 20% with Biden at 20%.