INDIAN WELLS, Calif. — The Koch-backed political juggernaut that helped fuel political opposition to the Affordable Care Act will now deploy its resources in defense of the signature legislative accomplishment of the Trump era, aiming to provide cover for Republican lawmakers who backed a major tax overhaul in the face of stiff political headwinds.

Americans for Prosperity, the chief political arm of the network of public advocacy organizations founded by industrialists Charles and David Koch, this weekend reiterated the pledge it made last summer to spend upwards of $400 million to help boost likeminded candidates and incumbents in the midterm elections.

What’s changed in the six months since the Koch network last gathered is that the GOP-led Congress rebounded after a failed Obamacare repeal effort to see through legislation slashing corporate and individual tax rates.

The significant financial commitment — well beyond what the network spent in the 2016 presidential election and others before it — includes $20 million solely oriented toward promoting the new tax law’s benefits to a public that remains skeptical of the overhaul.

It’s the kind of full-throated defense that Democrats and their allies never mustered for the Affordable Care Act in 2010 when they lost their House majority and control of statehouses across the country. And it could be essential in the face of an energized opposition to Trump and his party that has Democrats optimistic they can turn the tables in 2018.

“It is not our Obamacare. It is a successful policy that’s driving growth,” Sen. Thom Tillis, R-N.C., the vice chairman of the Senate Republicans’ campaign committee, said at a dinner session Saturday night.

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Tim Phillips, the president of AFP, told reporters invited to cover the three-day gathering of 550 at a resort hotel near Palm Springs that the organization was “all-in” to defend what he called the Koch Network’s “policy majorities” in Washington and across the country. AFP boasts staff in 36 of 50 states that will be deployed to back their candidates.

“The left is energized. There’s no question about that,” he said. “It’s prudent for folks to understand that and acknowledge that, and say what do we need to do to make sure that we’re explaining to folks that agree with us that these are important elections.”

“All-in” was the credo of the weekend for a network celebrating what it said was the most significant period of achievement in its existence. Charles Koch talked of the national transformation he and his allies have helped usher in, and which they much amplify in the years ahead.

“We’ve made more progress in the last five years than I had in the previous 50,” Koch told donors at an evening reception. “My challenge to all of us is to increase the scale and effectiveness of this network by an order of magnitude. … If we do that I’m convinced we can change the trajectory of this country.”

The hundreds of donors participated in breakout sessions focused on how to exponentially grow the progress made not just in politics but on an array of other issues, including criminal justice reform, education and business development.

Beyond the tax overhaul, top Koch network officials touted the repeal of federal regulations and the confirmation of scores of new conservative judges. They pointed to even more progress at the state level, with budget reforms, tax cuts and the expansion of Right to Work and school choice policies.

Gov. Matt Bevin of Kentucky received a standing ovation Sunday afternoon when he ticked off dozens of policy initiatives he had achieved since taking office in 2015, many directly from the Koch playbook.

"The absolute enemy of progress is bureaucracy and regulation,” he said.

Left largely unmentioned was President Trump. The Kochs pointedly declined to spend money on the 2016 presidential race, focusing their efforts on downballot races. Charles Koch once referred to the choice between Trump and Hillary Clinton as akin to cancer or a heart attack.

And though officials reiterated their commitment to fully repealing the Affordable Care Act, more time was spent touting the tax changes. House Speaker Paul D. Ryan addressed attendees in a recorded video message, in which he called them the “unsung heroes” of enacting the tax legislation. He said priorities in the year ahead included welfare reform and criminal justice reform.

There was only tepid support for another presidential priority in 2018, a major infrastructure package, amid uncertainty over a primary funding source. Three of the lawmakers who addressed donors here ruled out any increase in the gasoline tax. Sen. John Cornyn of Texas, the Republican whip, noted some states have funded road projects through public-private partnerships but noted they have been controversial.

“It’s not going to fall like manna from the heavens,” he said. “We’re going to have to figure out how to do it.”