Democratic presidential candidate former Vice President Joe Biden speaks during a campaign stop at a Teamsters union hall in Pittsburgh, Monday.

PITTSBURGH — Joe Biden accused President Donald Trump of abusing the powers of his office and ignoring everyone but his political base Monday in his first public rally as presidential candidate, arguing in the crucial battleground state of Pennsylvania that strengthening unions and promoting social and economic unity can restore Democrats to the White House.

The former vice president told hundreds of supporters and labor activists that Saturday’s deadly shooting at a California synagogue proves anew that the country is “in a fight for its soul.” But he spent more time criticizing Trump for his political behavior than for the president’s past comments concerning white supremacists, unlike Biden’s video formally kicking off his presidential campaign last week.

“There’s only one thing that stands in our way. It’s our broken political system that’s deliberately being undermined by our president to continue to abuse the power of the office,” Biden said.

He called Trump “the only president who has decided not to represent the whole country. He has his base. We need a president who works for all Americans.”

Earlier in the day, Biden received the endorsement of the International Association of Fire Fighters, and many in the crowd wore union T-shirts and carried signs supporting him. They repeatedly interrupted him with cries of “We want Joe!” and the candidate declared: “I make no apologies. I am a union man” to sustained applause.

Biden’s 40-minute speech swung from vows of union solidarity to broadsides against Trump, but lacked the sharp focus on the president that marked his campaign announcement video last week.

Instead, Biden on Monday returned to his familiar, folksy pitch to working class voters and avoided the sweeping, liberal policy proposals embraced by much of the rest of the crowded 2020 Democratic field.

Biden promoted incremental steps to shrink college costs and expand health care access, unlike some rivals who have called for free or debt-free college and universal, government-run health care, paid for with significant tax increases.

“We can do all this without punishing anybody,” Biden said,

Trump, meanwhile, stepped up his criticism of Biden and boasted on Twitter about his own strong support among union members before Biden offered his pro-union message in Pittsburgh.