Americans for Prosperity said Saturday that its network would spend more than $400 million on conservative causes and candidates during the 2018 midterm election cycle — 60 percent more than during the 2016 presidential election period.

"We're all in," AFP President Tim Phillips told The Hill at the group's winter gathering at the Indian Wells resort in California.

He noted that the $400 million is the largest amount AFP has spent in an election cycle.

Republicans will be working hard to maintain its majorities in the House and Senate, Phillips said.

The cycle is "going to be a challenging year" for the party, he said.

AFP serves as the umbrella for a vast network of groups affiliated with the billionaire industrialists Charles and David Koch.

The organization sat out the 2016 presidential race between President Donald Trump and Democrat Hillary Clinton, though it spent heavily on Republican candidates and conservative causes, according to the report.

Some of the $400 million slated for this year will be spent on electing Republican candidates, as well as on promoting tax reform and other GOP achievements, including President Trump's judicial selections.

Hundreds of top conservative donors affiliated with Koch network are attending the California gathering.

"We’re looking for candidates, policy-makers who can credibly commit to helping people improve their lives," Brian Hooks, co-chairman of the Winter Seminar, told the Hill.

The Koch network spent $20 million on lobbying for the Republican tax-reform bill and will put out another $20 million to tout its benefits, Hooks said.

"We're hopeful," Phillips said. "When you look at recent coverage of the public’s view of tax reform, it's going up as they see pay raises."