Jamaal Bowman was a teenager living in a rent-stabilized apartment on Manhattan’s Upper East Side when Donald Trump placed full-page ads in the city’s major newspapers calling for the reinstatement of the death penalty after the arrests of the Central Park Five.

Trump’s tactics have changed little since then, Bowman says, but he feels they are far more dangerous coming from the White House than from a Fifth Avenue penthouse.

So, frustrated by what he views as a “lack of urgency” on the part of Democratic leaders, the middle school principal is now mounting a longshot bid to unseat his own congressman, Eliot Engel, a 30-year House veteran Democrat and chair of the foreign affairs committee.

“Donald Trump has built his entire career on being a bully, and how do you confront a bully? You punch him in the mouth,” Bowman said in a recent interview. “You have to show the American people that you’re willing to take on a demagogue bully in the White House, and right now that’s not happening.”

The contest to represent Engel’s deep-blue district is part of a progressive rebellion against some of the most powerful Democrats in Congress by insurgents in the party who believe the lawmakers have not gone far enough to hold the president accountable. Inspired by the success of the congresswomen Alexandria Ocasio-Cortez and Ayanna Pressley in 2018, and hoping to tap into growing disenchantment with the status quo, these challengers are part of a leftwing strategy to turn safely Democratic districts into staging grounds for a broader fight over the future of the party.

Now Engel is one of a growing slate of senior House Democrats facing primary challenges from candidates similar to Bowman: young, diverse and more ideologically aligned with the activist left.

Bowman has earned the backing of the Justice Democrats, the leftwing group that recruited Ocasio-Cortez as part of its campaign to unseat “corporate Democrats”. Their endorsement could turn the race into a test of strength for insurgent groups trying to reshape the Democratic party by taking on the entrenched establishment.

“We’ve already seen how a handful of Democrats like ‘the Squad’ entering Congress has moved the center of debate on climate policy, healthcare, immigration, foreign policy and racial justice,” Waleed Shahid, a spokesman for the Justice Democrats, said, referring to a quartet of progressive lawmakers that includes Ocasio-Cortez, Pressley, Rashida Tlaib and Ilhan Omar. “The goal is to make the Democratic party work for its base.”

In total, Justice Democrats have endorsed eight Democratic primary challengers – all of whom reject money from corporate political committees and support progressive issues like Medicare for All and a Green New Deal.

Their first target this cycle was the Texas congressman Henry Cuellar, one of the most conservative Democrats in Congress who will face the progressive immigration lawyer Jessica Cisneros. Justice Democrats also joined a coalition of prominent liberal groups in backing Marie Newman against the Illinois congressman Dan Lipinski, one of only a few national Democrats opposed to abortion rights.

Shahid believes the primaries are already having an impact.

Before Congress recessed for August, Engel announced his support for a formal impeachment inquiry and emphasized the work his committee was doing to investigate any “possible acts of wrongdoing in the executive branch”.

Bowman welcomed the shift but wondered why it had taken so long.

Jerry Nadler, second from left, and Eliot Engel, third from left, are among Democrats facing primary challenges. Photograph: UPI/Barcroft Media

The House leadership’s cautious approach on impeachment has certainly given primary challengers an opening to go after top Democrats. But many of the candidates running primaries from the left are also focused on policy issues, from Medicare for All to affordable housing and rising income inequality.

Defeating an incumbent member of Congress in a primary is extremely rare. Of the 176 House Democrats who sought re-election in 2018, only two lost their primaries – New York’s Joe Crowley, the No 4 House Democrat who was unseated by Ocasio-Cortez, and the 10-term Massachusetts congressman Michael Capuano, who was defeated by Pressley.

In an effort to protect incumbents and avoid such divisive primaries, the Democratic Congressional Campaign Committee (DCCC) introduced a new policy prohibiting vendors from working with candidates running against sitting members of Congress. But the rule – which progressives have likened to a consultant “backlist” – has done little to stop the wave of challenges to entrenched House Democrats.

Progressive activists see particular opportunity in New York’s 16th congressional district because Engel, like Crowley and Capuano, is a long-serving white congressman representing an electorate where the majority of voters are nonwhite.

Arnold Linhardt, a consultant for Engel’s congressional campaign, said the comparisons are superficial.

“Don’t forget that while Joe Crowley was losing in Queens, Congressman Engel was winning his primary with 74% of the vote,” Linhardt said. He added that the voters in the district had re-elected Engel multiple times and that the congressman has a long record of supporting progressive causes.

Bowman, who is black, said that this moment demanded “bold” leadership – and not a “paper progressive”. He argues that he brings a different lens to the challenges facing the district and the country because he’s experienced them – as a child in public housing, raised by a single mom, and as an educator in the Bronx, teaching students growing up in circumstances far more difficult than his own.

His message to voters: “Change is coming to New York’s 16th district and to Washington.”

Tiffany Cabán’s race for Queens district attorney galvanized progressives around the country. Photograph: Jeenah Moon/Reuters

New York has emerged as a central battleground for Democrat-on-Democrat fights. In addition to Engel, the House judiciary chair, Jerry Nadler; appropriations committee chair, Nita Lowey; and congresswomen Carolyn Maloney and Yvette Clarke all face multiple primary challengers. Elsewhere, House Speaker Nancy Pelosi and House majority leader Steny Hoyer, the No 2 Democrat, have also drawn primary opponents.

Like the Tea Party and Republicans, the progressive wing is trying to push Democrats left on policy while seeking to sever its ties to Wall Street and special interests. After the 2018 midterms, which saw progressive candidates struggle in moderate and battleground districts, some activists argued the best targets are Democratic strongholds.

“The future of the progressive movement is going to be decided in safe, blue districts like New York,” said Sean McElwee, a co-founder of the progressive thinktank Data for Progress.

“For so long, primaries were seen as a terrible idea,” he continued. “But after AOC won, running a primary doesn’t seem like such a terrible idea anymore.”

And now, no Democratic giant is seen as too big to slay.

“The message from Crowley’s defeat was clear: if you do not change your behavior, you might lose your job,” said Hank Sheinkopf, a veteran Democratic strategist based in New York.

He said incumbents would be wise to take their primary threats seriously, pointing to the primary race for Queens district attorney that pitted the democratic socialist Tiffany Cabán against the Democratic borough president, Melinda Katz.

The race galvanized progressives around the country and rattled establishment Democrats across New York. After a weeks-long recount, Katz ultimately defeated Cabán by a few dozen votes.

“It’s hard to call it a loss when it never should have been that close in the first place,” Sheinkopf said.

Even in defeat, progressives say primary challenges have yielded results.

In 2016, Bernie Sanders lost to Hillary Clinton but succeeded in popularizing leftwing ideas such as Medicare for All, a $15 minimum wage and tuition-free public college. He is now a leading contenders for the 2020 Democratic nomination.

This year, the New York governor, Andrew Cuomo, signed into law a batch of progressive policy priorities even though he easily defeated Cynthia Nixon, the actor and activist who mounted an insurgent campaign to challenge him from the left.

“We lost that election by a lot but our entire agenda won,” said Rebecca Katz, a progressive strategist and a former senior campaign adviser to Nixon.

Now Katz is working with Alex Morse, the 30-year-old, gay mayor of Holyoke, Massachusetts, who is running to unseat the congressman Richard Neal. Neal, chair of the House ways and means committee, was first elected to Congress in 1988 – before Morse was born.

“We have a member of congress who has been there for 30 years and is the chair of a powerful committee but you would never know it when you look at outcomes in the district,” Morse said in an interview.

He accused Neal of slow-walking the process to obtain Trump’s tax returns. Neal did subpoena them in May, and in July his committee filed a lawsuit to enforce the subpoena in court. But Morse said the delay was “emblematic of his lack of leadership”.

Peter Panos, a spokesman for Neal’s campaign, said the congressman had been “on the front lines of holding the Trump administration accountable”, including leading the effort to obtain the president’s taxes.

Morse says he won’t be deterred.

“When I ran for mayor at 21, people told me to wait my turn, to run for something else or to not run at all,” he said. “But I ran because people had given up on Holyoke. They thought their best days were behind them. That’s the same sentiment that exists here all across this district.”