The Koch brothers and their powerful donor network worry that Donald Trump’s behavior is obscuring his achievements and jeopardizing Republicans’ chances of success in this year’s midterm elections.

That was the message coming out of a private retreat in the California desert this weekend.

“President Trump is not helping get many Republicans elected,” said Tom Shepherd, a Cincinnati-based businessman who joined roughly 550 Koch donors in Indian Wells.

“I think he’s doing more harm than good because he’s distracting people from the good work which is happening, which is either happening because of him or in spite of him.”

The Kochs are beginning to implement their strategy to protect Republican majorities in the House and Senate in November.

The GOP has no more powerful ally than the Kochs’ vast political and policy network, which has long been demonized by the left and revered by the right for its short- and long-term efforts to reshape US politics and culture.

In California, the Koch network’s chief lieutenants renewed their vow to spend up to $400m on politics and policy relevant to the midterms.

That would be more than the combined resources spent by the Republican National Committee, the NRA and the Chamber of Commerce in the 2016 election cycle.

The Koch network’s 2018 investment includes $20m to help sell the recent tax overhaul to a skeptical American public through a series of public rallies, phone banking and paid advertising.

Despite the extraordinary investment, the men and women who filled the luxury resort outside Palm Springs acknowledged a difficult road ahead.

Some blamed history more than the regular distractions from Trump. The party in the White House traditionally struggles in the first midterms of a new presidency.

“It’s a challenge regardless of the president,” said Tim Phillips, president of the Kochs’ political arm, Americans for Prosperity.

But the donors who pledged at least $100,000 this year to the Koch network – there were an estimated 550 on hand – were less cautious when asked about the president’s leadership.

Many opposed his candidacy before the 2016 election. The Kochs themselves refused to endorse Trump.

“I didn’t support him,” said Frank Baxter, a retired investment banker from California who was ambassador to Uruguay under George W Bush. “The results are kind of changing my mind.”

Like others, he praised the tax overhaul, Trump’s judicial appointments and regulatory cuts. He added: “I still don’t like what he says or does.”

Gary Lynch, whose Iowa livestock business employs roughly 700 people, said he and his business have benefited from the tax overhaul. He said, however, that Trump’s behavior “doesn’t help” his party promote the benefits of the plan.

“He hasn’t got it down yet,” Lynch said, noting that he doesn’t mind Trump’s style personally.

Democrats need to pick up at least 24 seats to claim the House for the last two years of Trump’s first term. Recent wins in Alabama and Virginia, backed by Trump’s low approval ratings, suggest the GOP is in trouble.

Asked about his party’s 2018 prospects, congressman Mark Meadows, of North Carolina, one of a handful of elected officials who attended the Koch conference, acknowledged that the House majority is at risk.

“I can make the case for losing 18 seats and no more” he said. “I can make the case for 28 seats. It’s a long ways off. It depends what we do between now and November.”

At the Koch retreat, Trump donor Doug Deason said he enjoyed the president’s social media habits, which he said allowed him to speak directly to the people.

“I don’t think it helps. I don’t think it hurts,” Deason said. He noted that the Koch network would “spend a lot of money” to ensure the benefits of the tax overhaul aren’t overshadowed by any distractions.

“Who gives a crap about Jay-Z?” Deason asked. “I don’t.”