The episode represents the latest crack in a long-standing but unofficial policy on Capitol Hill to not get involved in primaries featuring incumbents. And the trend is not just limited to Democrats. An increasing number of House Republicans — including some GOP leaders — have grown more comfortable this cycle picking sides in races where they feel it’s urgent to intervene.

Now lawmakers, aides and strategists in both parties say the pattern will be difficult, if not impossible, to reverse. It’s a shift that reflects the ideological — and anti-establishment — churn taking place in the Donald Trump era, and it’s sparking concern among the old guard about rising intraparty warfare.

"More and more members of Congress are going to look and say 'rules are rules' but if in fact there’s a district that’s suffering… we’re going to see a lot more members of Congress supporting challengers,” said Marie Newman, who knocked off longtime Illinois Democratic Rep. Dan Lipinski earlier this year with the backing of several prominent Democrats.

Even as leaders in both parties have tried to paint any decision to wield influence in primaries as a “special” case, younger firebrands are interpreting their leadership’s involvement as a green light to show support and spend money on the challengers they prefer.

“If the establishment is going to start shooting at the outsiders and the pro-Trump elements of our caucus, then the bullets aren’t only going to be flying in one direction,” said Florida Republican Rep. Matt Gaetz, who backed the successful GOP challenger to Rep. Ross Spano (R-Fla.) after a member of GOP leadership targeted one of his other colleagues.

Playing in primaries has long been looked down upon in both the Republican and Democratic Party, where leaders deploy multi-million-dollar campaign arms to shield incumbents and squash any potential challengers. The Democratic Congressional Campaign Committee took it a step further this cycle — enforcing a “blacklist” of vendors who work for candidates seeking to oust sitting lawmakers, a move that outraged progressives and motivated them to get even more involved in primary campaigns this cycle.

“These places operate on members’ dues,” said Brendan Buck, a GOP strategist, referring to the parties’ campaign arms. “To be able to get members to contribute, they need to convince them it’s an incumbent protection operation.” Otherwise, he added, “that trust is eroded” and “the money stops coming in.”

Plus, it’s dangerous to take a shot and miss. Leadership used to even shy away from open primaries amid fears of picking the wrong candidate and alienating a future colleague.

“It’s a risky play, no doubt,” said Buck, who served as a top aide to former Speaker Paul Ryan (R-Wis). “You better be damn sure it’s gonna work if you’re gonna do it. People have long memories.”

But now, insurgent lawmakers angry with the establishment and tired of abiding by the kind of decorum that once governed Washington are looking to flex their muscles in primaries — and put leadership on notice.

“No one gets to complain about primary challenges again,” Ocasio-Cortez tweeted in response to Pelosi’s endorsement of Kennedy. The freshman lawmaker, who has won the ire of some colleagues for her openness to supporting primary challenges, also called on the DCCC to get rid of its vendor blacklist. “It seems like less a policy and more a cherry-picking activity,” she wrote.

This is hardly the first time rank-and-file lawmakers have engaged in primaries — although many more are openly doing so this year — but it’s now easier than it was a decade ago to actually wield influence through the use of grassroots fundraising and social media.

“The old ways of Washington empower leadership through money. But we’re starting to see that the message and movement may be more important than money,” said Gaetz, who swore off PAC funding. “In today’s world of social media, digital communication and wall-to-wall cable television, the leadership no longer has a stranglehold on the brand or the messengers.”

The 2022 cycle may offer further opportunity for insurgents, as incumbents may be facing entirely new constituencies after the latest round of redistricting.

Allies of Pelosi have defended her decision to back Kennedy, arguing the speaker did not undermine her policy of fiercely protecting House incumbents since she was weighing in on a Senate race. Progressive lawmakers and strategists have dismissed that explanation.

“What we’re seeing right now is the Democratic establishment really being honest in public about what they’re doing. What’s not a change is them taking sides in primaries — they have long done it for years and years and years, they’ve just been more private about it,” said Charles Chamberlain, executive director of Democracy for America.

Ocasio-Cortez, who declined to be interviewed for this story, shot to prominence after toppling one of the most powerful Democrats in the House: Joe Crowley, the Democratic Caucus chair who was often mentioned as a potential future speaker. A fellow member of her liberal “squad,” Rep. Ayanna Pressley (D-Mass.), took down longtime Rep. Mike Capuano in 2018 and has since backed other primary challengers.

Progressive challengers have already unseated several long-entrenched Democratic incumbents this year, including Lipinski, House Foreign Affairs Committee Chair Eliot Engel in New York, and Rep. Lacy Clay in Missouri.

If Neal is defeated by Holyoke mayor Alex Morse, it would be a huge victory for Ocasio-Cortez and a disappointment for Pelosi. The speaker spent several minutes praising Neal’s progressive bona fides at a news conference Thursday and said his district would suffer “a tremendous loss” if he’s ousted.

In February, Ocasio-Cortez launched her own political action committee, which has backed primary opponents of Neal, Engel and Lipinski. Other progressives, including Pressley, Sens. Bernie Sanders (I-Vt.) and Elizabeth Warren (D-Mass.), and Reps. Pramila Jayapal (D-Wash.), Mark Pocan (D-Wis.), Ro Khanna (D-Calif.) and Katie Porter (D-Calif.) are among the lawmakers to endorse challengers to their colleagues this cycle.

Waleed Shahid, communications director for the left-leaning Justice Democrats, pointed out that several prominent Democrats — including Engel — actually came to Congress by defeating an incumbent Democrat. Pelosi’s endorsement of Kennedy, whether she intended to or not, “will create more room and space for incumbents to endorse in primary challenges,” he added.

“Primary competition has to happen when a party is struggling to define itself,” Shahid said. “What primaries literally are, are places to define what it means to be a Democrat or what it means to be a Republican.”

On the GOP side, lawmakers were eager to boot controversial Iowa Rep. Steve King, who has made racist remarks and came close to losing his general election last year. Five House Republicans donated to his successful primary opponent, Randy Feenstra: Rep. Steve Stivers, the former head of the House GOP’s campaign arm; retiring Rep. Paul Mitchell, who was a member of GOP leadership at the time; retiring Rep. Will Hurd, the lone black Republican in the House; and Reps. Adam Kinzinger and Dusty Johnson.

Gaetz, meanwhile, said he wasn’t planning to get involved in Spano’s race. But after GOP Conference Chair Liz Cheney (R-Wyo.) backed Rep. Thomas Massie’s (R-Ky.) Republican opponent — something Gaetz confronted Cheney about during a private conference meeting — he said it is clear they are now “free agents.”

Cheney and Rep. Mike Turner (R-Ohio) later pulled their endorsements of Massie’s challenger, Todd McMurtry, after his old racist tweets resurfaced. But Cheney argued during the closed-door meeting that Massie was a “special case,” pointing out that Trump himself has called for him to be thrown out of the party. And Cheney has supported other colleagues facing competitive primaries.

Gaetz maintains that he isn’t trying to become a major player in contested primaries, noting he didn’t get involved until late in the cycle and focused on his home state of Florida. The two-term lawmaker also said he is focused on getting Trump reelected and only backed Spano opponent Scott Franklin because he would better boost the president’s agenda. He called Spano — who is under investigation by the DOJ for possible campaign finance violations — a “flawed” candidate.

But both Gaetz and Ocasio-Cortez have serious sway on the right and left, respectively, so if they do decide to get more involved next cycle, things could get messy. Several other Gaetz-backed candidates sailed to victory in open Florida GOP primaries last week, including far-right activist Laura Loomer who has been banned from Twitter and Facebook for racist comments and attacks on Islam but who has little shot at winning in November.

“One of the jobs of leadership is to keep the peace amongst your team. A real quick way to have your team fall apart is if there is suspicion that certain members are trying to unseat other ones,” Buck said. “Politics is a team sport. And if your team devolves into this type of fighting, it’s really hard to put that back together.”