Elizabeth Warren delivered a rallying cry to Democrats in the wake of Donald Trump’s election victory, calling on the party to show it stands ready to “unrig this economy” as the president-elect works with billionaires to overhaul it.

Calling on allies to “learn the right lessons” from Kamala Harris’s defeat last week, the Democratic senator set the stage for a “big battle” over economic policy as Trump returns to the White House.

“Is it going to be a handful of billionaires? We know what kind of policy they want to set,” she said. “Or are we going to show voters that Democrats are the ones who are willing to unrig this economy?”

Warren insisted that the fight against monopolies dominating the US economy, which Joe Biden made clear he wanted to take on as president, “does not die” when he steps down in January.

“It only dies if we roll over and play dead,” she said. “And I don’t know about you, but I don’t plan to do that.”

The senator appeared alongside a string of senior progressive leaders, including fellow senators Bernie Sanders and Amy Klobuchar, at an event on Wednesday dubbed Delivering for the Working Class.

“Never before in American history have so few multibillionaires had so much wealth and so much economic and political power,” said Sanders. “And let me tell you, these are not nice guys. They may come off as nice guys. They may make contributions to the local hospital or [the] Boys & Girls club. But they are very, very, greedy people.

“The antidote to enormous economic and political power on the part of the few is mass organizing at the grassroots level among working people – to stand up and fight for an economy that works for all.”

Trump has outlined plans for a series of significant economic changes, pledging to cut taxes and impose sweeping tariffs on foreign imports. While he has promised to bring down prices for Americans, economists have warned that some of his proposals risk exacerbating inflation.

Republicans who have publicly supported policies designed to hold corporate power accountable must now themselves be held to account, Klobuchar said: “I want to see some action on their side, and that also depends on who they put in office.”

The president-elect has yet to appoint some of his most important economic officials, including treasury secretary and chair of the Federal Trade Commission.

Wednesday’s event focused on why Democrats must continue standing up for working-class Americans by pushing pro-competition laws and aggressive antitrust enforcement in the next Congress, when Trump is set to take office with a Republican majority in the Senate and probably also in the House.

Nidhi Hegde, the director of Fight Corporate Monopolies, a progressive group, cited several policy efforts made in recent years in challenging concentrated corporate power in introducing the event, including holding Wall Street firms accountable for fixing rent costs.

“Over the next four years, we need to protect these initiatives and the progress that we’ve made, and challenge the incoming administration to deliver for working families as we continue the fight against billionaires and monopolists who control the American economy,” said Hegde.

Sanders said the most important issues facing the American public were scarcely discussed in political campaigns, citing issues such as the climate crisis, the broken healthcare system, the housing crisis and bigotry. Among these unaddressed issues, he said, was the rapid movement toward oligarchy in the US.

“When we talk about oligarchy, it’s not only massive income and wealth inequality. It is not only the stagnation in wages for working-class people. It is also a massive increase in concentration of ownership,” said Sanders.

“You have in sector after sector, whether it is agriculture, whether it is transportation, whether it is financial services, whether it’s healthcare, whether it’s media or … youth sports, what you’re seeing is fewer and future fewer large conglomerates owning what is produced; and [controlling] the conditions that they are produced, and [what] the workers are paid, and the prices we pay for those goods.”

In a post on X in the aftermath of the election, the senator Chris Murphy, who also attended Wednesday’s event, noted that the Democrats won the majority of the highest median-income states, while losing the vast majority of low-income states this election.

“Yes, race and gender play a big role in politics,” he wrote. “But the hard truth is this – Democrats clearly aren’t listening to the people we say we fight for.”