WASHINGTON — For the moment, U.S. Sen. Cory Gardner isn’t backing the health care plan that fellow Republicans in his chamber unveiled Thursday — a caution that could spell trouble for the long-awaited legislation.

Hours after its release, Gardner said in a statement that he was “carefully reviewing” the 142-page proposal. In an interview later that day, the Colorado Republican said he wasn’t sure whether he would vote for it, and he suggested that Senate Majority Leader Mitch McConnell, the Senate’s top Republican, consider abandoning his goal of holding a vote next week on the legislation.

“If we can have opportunities to make the bill better, then by all means let’s take every chance and (all the) time we can,” said Gardner, who threw out of the idea of lawmakers working through the upcoming July 4 break. “I would be OK with spending our entire recess here.”

Gardner’s hesitancy is notable for several reasons. As chairman of the National Republican Senatorial Committee, he is one of the top GOP officials in the Senate — a position that puts him alongside McConnell during weekly Republican news conferences outside the chamber.

The Colorado lawmaker also was among 13 Republican senators initially tapped to help shape the legislation — though Gardner said his role was limited to providing broad input rather than crafting the actual text.

“This is the first I’ve viewed the legislation, so I am beginning to carefully review it as we continue to look at ways to rescue Colorado from the continued negative impacts of the Affordable Care Act on our health care system,” Gardner said in a Thursday statement.

Finally, Gardner has campaigned for years on the promise of repealing the Affordable Care Act, also known as Obamacare — a program Colorado policymakers have embraced and one that has done well in recent polling.

If McConnell can’t keep Gardner’s support, then its chances of passage are slim.

To get it through the upper chamber, the GOP needs a minimum of 50 votes. And with 52 Republicans in the Senate — and Democrats expected to unite in opposition — that means McConnell can lose no more than two members of his party to succeed.

That challenge came into focus Thursday as four Senate Republicans — Ted Cruz of Texas, Ron Johnson of Wisconsin, Mike Lee of Utah and Rand Paul of Kentucky — released a statement saying they aren’t ready to vote for the bill but are willing to negotiate.

The varying reactions Thursday among Senate Republicans highlight the difficult balancing act between conservative Republicans who want to wipe out the Affordable Care Act and those who want to preserve some elements, such as consumer protections for patients with pre-existing conditions.

A critical issue for Gardner has been the topic of Medicaid.

Under the Affordable Care Act, Colorado expanded the number of residents covered by Medicaid and in the process cut the number of Coloradans without health insurance from nearly 15.8 percent in 2011 to 6.7 percent in 2015, according to the Colorado Health Institute.

The plan passed by the House Republicans in May would end that expansion in 2020; the Senate version also would unwind that expansion, though more slowly, while capping federal funding for Medicaid, which provides insurance for low-income residents and those with disabilities.

Gardner previously has urged caution about the speed in which the Medicaid expansion is rolled back — though he hasn’t said Republicans shouldn’t do it. It’s also one area where Gardner has provided significant feedback to the bill-writing team.

“I want to dig into the language,” Gardner said Thursday when asked whether he was happy with how the proposal dealt with Medicaid beneficiaries.

How he addresses that issue in the days ahead will be telling. McConnell has targeted next week for a vote but said the legislation would be open to changes beforehand.

Gardner said one area where he believed he made a difference in the plan was ensuring that children with disabilities or medically complex cases were exempt from a proposed limit on Medicaid spending.

That effort was applauded by officials at Children’s Hospital Colorado, though they took issue with the general thrust of the Republican proposal.

“Children’s Hospital Colorado urges Sen. Gardner to keep his public and repeated pledge of ‘stability’ for the Medicaid population,” Jena Hausmann, its president and CEO, said in a statement. “For the Colorado children who were covered by Medicaid before Obamacare and who will lose coverage if this hastily drafted plan becomes law, this approach is a far cry from stability.”

Another consideration is how analysts with the nonpartisan Congressional Budget Office “score” the bill by its cost and effect on the insurance market. The House version — which bears similarities to the Senate proposal — would reduce the federal deficit by $119 billion but lead to the loss of insurance for 23 million Americans by 2026, according to the CBO analysis.

“My strong initial impression is that it is essentially the same as the House bill,” said U.S. Sen. Michael Bennet, D-Colorado.

Bennet said he expected the forthcoming CBO score to show that “millions of people are going to lose their health insurance under this legislation.”

He described the bill-writing process as “lousy” and pointed to the secrecy as evidence that McConnell didn’t want Democratic input.

“I don’t believe Mitch McConnell has any interest in a bipartisan solution,” Bennet said. “He wouldn’t even share his draft with his own colleagues until today.”

There are political ramifications for both Gardner and Bennet on the issue of health care, though the topic will hit home sooner for Gardner.

The Republican lawmaker has been a longtime critic of the law, and he began his successful 2014 run for Senate with a pledge to repeal the health care initiative.

Among Republicans, there’s an expectation he will follow through on that promise, a desire driven by the law’s mandates and fines, as well as recent rate increases for Coloradans who buy their own health insurance (although many qualify for subsidies under the Affordable Care Act).

Recent polls, however, have shown support for the law in Colorado, a state that supported Hillary Clinton in her failed presidential bid against Donald Trump.

Depending on what happens to the legislation, it could be a critical issue for Gardner headed into his 2020 re-election — a race in which he would share the ballot with Trump.

Gardner will get a head start on that effort Friday, however, as Vice President Mike Pence is scheduled to attend a fundraiser for him during a visit to Colorado.