COLORADO SPRINGS, Colo. — Just days before an expected Senate vote on the Republican health care plan, the leaders of the Charles and David Koch network had few words of praise for the GOP bill.

Top aides of the organization at a retreat in Colorado Springs over the weekend said they are “disappointed” with the bill’s contents because, in their view, it doesn’t do enough to dismantle the Affordable Care Act but say they are working to make it better.

“At the end of the day, this bill is not going to fix health care,” said James Davis, a spokesperson for the Koch network, an affiliation of groups run by the politically active billionaire businessmen.

The semi-annual gathering brought together donors who contribute at least $100,000 per year to the upscale Broadmoor resort at the foot of the Rocky Mountains to discuss policy — and the next campaign.

The organization plans to spend between $300 and $400 million on politics and policy in the 2018 mid-term election, which is more than the network spent in the 2016 election when they stayed on the sidelines of the presidential election because of their distaste for then-candidate Donald Trump. The organization, however, has spent the past three election cycles drumming up opposition to Obamacare and running campaigns against it.

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While panels here included a broad range of their conservative and libertarian policy and political priorities, and fundraising for them, health care was a persistent topic.

Attendees include six senators and five House members who mingled among the nearly 400 donors over the course of the three-day event. Five of the six senators in attendance have said they are either undecided or opposed to the Senate GOP's Better Care Reconciliation Act as it is currently written.

Sen. Ben Sasse of Nebraska, a repeat guest of the Kochs, participated in a discussion open to the press where he was asked by the moderator if he’d support the Senate bill. Sasse demurred, saying, “The press is here, right? I have nothing to announce.”

Sasse admitted to dodging the question, telling the moderator who noted his evasiveness, “I was actually ducking, but whatever” to laughter.

Sasse did express some of his concern with the bill, saying that it doesn’t take into account employee mobility in the health care system. He said that he also hasn’t finished reading the 143-page bill and said it’s little more than a “Medicaid reform package.”

Just days after Senate Majority Leader Mitch McConnell unveiled his plan that repeals all of Obamacare's taxes on the wealthy and the health insurance industry and dramatically cuts Medicaid, the organizations under the Koch umbrella remain largely opposed to it because of the subsidies for people to purchase insurance and, they say, it doesn't do enough to rid insurance companies of coverage requirements.

They vowed to challenge Republicans who don’t support their objectives.

“Our network voraciously opposed Medicaid expansion in state after state,” said Tim Phillips, head of Americans for Prosperity, during a session with reporters who had to be invited to attend.

“These Republicans who expanded Medicaid were flatly wrong,” Phillips added, referring to Govs. Brian Sandoval of Nevada and John Kasich of Ohio among others. “So we’re going to continue holding these Republicans accountable.”

Related: Senators Urge Slowdown on Senate Health Care Vote

Two senators in attendance, Cory Gardner of Colorado and Jeff Flake of Arizona, have pressing concerns about the politics of health care when it comes to 2018. Flake is expected to have a difficult re-election campaign next year and Gardner is head of the campaign committee that works to elect Republicans to the senate and often attends the Koch retreats, which is a fruitful opportunity to recruit donors to the NRSC. Both have said they need to consult with their governors and stakeholders in their state before they decide how they vote on the measure that is likely to come up for a vote this week.

Others at the retreat included conservatives Sen. Mike Lee of Utah and Ted Cruz of Texas who both came out last week opposing the bill in its current form, taking similar positions as the Kochs.

Sen. John Cornyn, R-Texas, the second ranking Republican in the Senate, was also there. As the Republican whip, tasked with finding the votes to pass the measure. “It’s going to be close,” Cornyn told reporters here of the vote expected at the end of this week.

When asked if President Donald Trump was going to help pass health care this week, Cornyn said, "We’re trying to hold him back a little bit." A super PAC backing President Donald Trump and Vice President Mike Pence announced that they'd run a million dollar ad campaign against Republican Senator Dean Heller in Nevada after he announced his opposition to the health care bill.

Cruz was seen in deep discussion with Rep. Mark Meadows, R-N.C., who helped to usher in the a compromise amendment with moderate Rep. Tom MacArthur, R-N.J., that led to the passage of the House health care plan last month.

Meadows told a small group of reporters that he could support the Senate bill if changes were made, including a proposal by Cruz that would allow states to offer Obamacare plans along side non-compliant Obamacare insurance that lack robust coverage.

Cornyn said he’s been talking with Lee and Cruz to “address their concerns.”

The Koch network, through the non-profit Americans for Prosperity and the super PAC Freedom Partners, came out strongly against the House health care bill until changes were made that reduced requirements on insurance companies that they must offer robust, and in effect, more expensive health plans.

The Koch group has mixed reactions overall to the Trump administration. They praise his nomination of Neil Gorsuch to the Supreme Court and his effort at rolling back regulations and reforming the Veterans Affairs Department. But they are disappointed with their disinterest in moving forward on criminal justice reform.

Marc Holden, co-chair of the network, said that despite set backs with Jeff Sessions as attorney general, they’re “still grinding on it” at the federal level. Holden adds that there are a few allies within the Trump administration who support their bipartisan efforts to undo overly stringent sentences for nonviolent offenders and make it easier for convicted felons to re-enter society after time served.

"We’re still excited about the progress on Capitol Hill," Holden said, predicting that criminal justice reforms would get the support of 70 senators.

One of the featured guests at this seminar is former Dallas Cowboys player Deion Sanders. He partnered with Koch-backed Standing Together on a $21 million effort to fight poverty in Dallas.

“We’re going to make life so much easier for others,” Sanders said during a plenary session with Charles Koch. “It doesn’t take courage to stand with this man. It takes common sense to stand with this man.”