As Abba’s Dancing Queen played, Donald Trump walked across a lawn featuring cornhole, oversized Connect Four, a ferris wheel and a food tent offering short ribs, mac and cheese and apple pie. Members of Congress and their families had come for the annual White House picnic. But not every member of Congress.

Missing the fun was Thomas Massie, a longtime thorn in the US president’s side. Massie was at home in Kentucky, suffering a primary election defeat that made him the latest victim of Trump’s revenge tour. “We won the Massie thing,” the president told guests at the picnic on Tuesday evening. “He was a bad guy. He deserves to lose.”

It was the latest imperious demonstration of Trump’s enduring stranglehold on the Republican party, and his determination to purify it of dissenters. But at what price? In his quest to consolidate power, critics say, the president could also undermine his own legislative agenda – and his party’s fragile majority on Capitol Hill.

Massie joins a growing list of purged Trump critics who now feel liberated to stir up trouble because they have nothing left to lose. The president also faces opinion polls suggesting that, while his support base remains as fervent as ever, it is losing touch with the middle ground where November’s midterm elections will be won and lost.

Charlie Sykes, a conservative author and broadcaster, said: “He’s tightening his grip on his party, for better or for worse. The problem is that most of his victories are coming at the expense of the Republican party rather than the Democrats at this point, which ought to be something of a warning sign.”

No slight is too small for Trump to wage a vendetta. During his first term, he ousted – or made life intolerable for – Republicans including Liz Cheney, Adam Kinzinger, Justin Amash, Bob Corker, Jeff Flake and Will Hurd. His second term is proving equally unforgiving to those deemed to have failed his loyalty tests.

In Indiana, five state senators lost their seats after resisting Trump’s demands regarding the redrawing of congressional maps. In Louisiana, the US senator Bill Cassidy lost his primary last weekend after voting to convict Trump in 2021, during the second impeachment trial.

In Kentucky, Massie lost the most expensive congressional primary in history against Trump’s handpicked challenger, former Navy Seal Ed Gallrein, after challenging the president on government spending, war powers and files on the convicted sex offender Jeffrey Epstein.

‘I’ve got seven months left’

Tara Setmayer, co-founder and chief executive of the Seneca Project, a women-led political action committee, said: “The fact that Donald Trump and his acolytes poured a record amount of money into the primary to take him out because he wasn’t sufficiently loyal enough to cover for Donald Trump on the Epstein issue tells you everything you need to know about the current state of the Republican party.

“America is watching. The world is watching and people will not forget who protected predators.”

Massie, however, was defiant in defeat. In his concession speech, he implied that he would push back even harder against Trump during his remaining time in office, saying of the Epstein Files Transparency Act: “We’ve taken out two dozen CEOs, an ambassador, a prince, a prime minister, a minister of culture – and that was just six months. I’ve got seven months left in Congress.”

Cassidy, also, could become a thorn in Trump’s side for the rest of the year on Capitol Hill. Less than 72 hours after losing his primary, the US senator abruptly threw his support behind a Democratic war powers resolution to force Trump to end the Iran war, helping push it through the Senate after seven previously failed attempts.

Meanwhile, the US senator Thom Tillis, whom Trump threatened with a primary challenge and who decided not to seek re-election, has broken from the president on various issues. Marjorie Taylor Greene, a one-time Trump ally who clashed with him over the Epstein files and quit Congress, is using her public platform to accuse the president of betraying his “America first” principles.

Yet still Trump is thirsty for vengeance. He has threatened to target Senator Rand Paul of Kentucky and the Colorado representative Lauren Boebert because of their support for Massie, branding Boebert “weak-minded” and “very difficult”. He also lashed out at the representative Brian Fitzpatrick of Pennsylvania for voting “against me all the time”.

‘You’re gonna need their votes’

Setmayer, a former Republican communications director on Capitol Hill, observed: “The irony of the circular firing squad now happening within Maga and the Maga offshoots is totally predictable, because Donald Trump cannot continue to demand blind loyalty from people who believed him and his promises, and then he betrays them and expects them to continue to kiss the ring.

“It doesn’t work like that. And so he is now beginning to reap the consequences of betraying so many leaders in his base. They see the writing on the wall. Donald Trump is a wounded animal and they are looking at their own long-term preservation because at some point there will be a world that doesn’t have Donald Trump in it.”

With razor-thin majorities in both the House and Senate, Trump needs the votes of the very people whose careers he has destroyed. He is already facing a rare rebuke from Republicans over his lavish White House ballroom project and a controversial $1.8bn compensation fund for allies claiming to be victims of “political weaponisation”.

Kurt Bardella, a former Republican congressional aide turned Democrat, predicts that Trump may come to regret burning his bridges with Massie and Cassidy, both of whom have voted with him on the vast majority of issues. “They’re still in office, and if you’re going to want to do anything for the rest of the calendar year, you’re gonna need their votes and you’ve just torched them,” Bardella said.

“Donald Trump may have won the battle, but I’m not sure he’s going to end up winning the war because these very men who have now every reason to stick it to him have the power to stop his agenda for the rest of the year and face no consequences because there’s no election hanging over their head any more. In that way, Donald Trump has empowered them and liberated them to vote their conscience.”

Trump faces a further, deeper problem in November’s midterm elections. While his crushing of internal dissent has proved he retains intense support within the party, his national approval rating has plunged to a record low of 37%, according to a New York Times newspaper/Siena poll, while Republicans trail Democrats 39% to 50% on the generic congressional ballot.

‘A catch-22 for Republicans’

Larry Jacobs, director of the Center for the Study of Politics and Governance at the University of Minnesota, Twin Cities, said: “Trump is as powerful as ever among the Maga sect within the Republican party, but that’s not going to help him come November.

“Trump’s influence and power in marshalling the Maga voters may well disadvantage Republicans in districts that are going to be competitive in a midterm election that is so clearly going to [be] hostile to Republicans and the president. Independent voters have been tremendously alienated and opposed to Trump and his policies and their effects and, even among Republicans, there are some troubling signs.”

Republicans are caught in a trap of their own making: Trump is their superpower in a primary, but could be their kryptonite in a general election. Sykes, author of How the Right Lost Its Mind, said: “He’s sending the message that if you cross him he will destroy you, at the very moment when Republicans, in order to survive the midterms, do need to distance themselves from Trump.

“If you’re a Republican, you not only can’t do the right thing, you can’t do the smart thing. You’re facing these massive headwinds, these crashing polls, a surge in the cost of living, and Trump is demanding absolute loyalty and has made it clear that if you try to move away from him, your political career as a Republican is over. It is very much a catch-22 for Republicans.”

Sykes pointed to the example of Trump’s decision this week to endorse the Texas state attorney general, Ken Paxton, who has been both impeached and indicted during a chequered career, in next week’s primary runoff against John Cornyn, the incumbent US senator widely seen as a safer bet against the rising Democratic star James Talarico in November.

Asked how Republicans would react to the decision, Trump told reporters: “They’ll be all right with it. They want to win. I know how to win. Some of them don’t know how to win. I know how to win. I think I’ve proven that, haven’t I?”

In truth, Republicans are mortified. Since Texas is a hugely expensive state in which to run a campaign, the cost of defending a Paxton candidacy would siphon money away from battleground states such as North Carolina, Georgia, Ohio, Michigan and Pennsylvania. Even if Paxton holds on, it would be a pyrrhic victory.

“It’s extraordinary. This is a guy who is absolutely scandal-infested,” Sykes said, of Paxton. “Arguably one of the most corrupt politicians in America, and Donald Trump just endorsed him to defeat a leading Republican incumbent senator. It means that obviously he’s prioritising personal loyalty over the Republican party.

“He’s never cared about the Republican party. But this was a pretty dramatic gesture.”