WASHINGTON (AP) — The Senate debate over health care has made it painfully clear: behind their self-confident "repeal and replace" slogan, Republicans were never united around an alternative to "Obamacare."

Rolling back a government program that's benefiting millions of people is hard enough — maybe next to impossible — but Republicans compounded their own difficulties with factional divisions, a president lacking a policy of his own, and mission creep that morphed into a Medicaid overhaul unacceptable to GOP governors.

Republican leaders say they remain confident they'll get a bill that clears Congress — but even they say they don't know yet how they'll do it.

Fallout from a collapse could endanger other GOP priorities such as overhauling the tax code, not to mention basic government functions like keeping agencies running or raising the federal borrowing limit.

Health care was supposed to be relatively easy, with Republicans controlling both the White House and Congress.

Hoping to score a quick legislative victory on repealing and replacing the Affordable Care Act, Republicans went behind closed doors to hammer out their own proposals. But that ignored the complexity of the health care industry, and powerful interest groups including hospitals, doctors, and insurers were alienated. The strategy foreclosed chances of co-opting any Democrats, some of whom share concerns about high premium and shaky insurance markets.

As polls showed alarmingly low public support for their legislation, Republicans only doubled down, with President Donald Trump threatening retribution for lawmakers who break ranks.

The result: Republicans have managed to "make more popular a policy that wasn't very popular when we started trying to get rid of it," said Sen. John McCain, R-Ariz. The lack of bipartisanship on health care was an object lesson in McCain's impassioned floor speech upon returning to the Senate following a cancer diagnosis.

It was easy for Republicans to oppose "Obamacare" when their party did not bear responsibility for governing. But now that they're in power, they haven't been able to coalesce around an alternative. Instead Republicans are divided in three broad groups.

Some would make revisions to Obama's law, diluting or replacing unpopular provisions and rebranding that as "repeal." Others, fiscal conservatives, viewed the debate over the ACA as the springboard for bigger curbs to government health insurance programs like Medicaid and Medicare. A third group remains philosophically opposed to government involvement with health care, arguing that a true market will only emerge when individuals bear more responsibility for costs.

The three strands are visible in proposals that Majority Leader Mitch McConnell tried to steer through the Senate, ranging from limited repeal of "Obamacare" provisions, to a broader repeal, to various ideas for replacing components of the ACA. While Obama's law extended coverage to some 20 million people, nonpartisan analyses estimate the GOP proposals would make millions more uninsured.

Similar kinds of divisions could emerge on other issues, particularly if the health care debate leaves Republicans nursing grievances against one another.

During the 2016 presidential campaign, many Republicans hoped a consensus plan would be forged, and some GOP candidates offered detailed proposals. But Trump never delved deeply into health care, and his plan was basically a collection of talking points. At times, he sounded more like a Democrat, calling for Medicare to negotiate prescription drug prices, and promising "insurance for everybody."

"He is obviously working this from a political standpoint; what I don't see is him working it from a policy standpoint — fashioning that compromise for all Republicans," said Dan Mendelson, CEO of Avalere Health, a consulting firm. "There's no evidence of thought leadership."

Trump hinted at one point earlier this year that he'd unveil his own health care plan, but that didn't happen. The congressional plans that followed drove a wedge between Capitol Hill Republicans and GOP governors. The main reason: Medicaid mission creep.

Beyond repealing Obama's expansion of Medicaid, congressional Republicans proposed to limit overall federal financing for the federal-state program that covers more than 70 million low-income people. Medicaid recipients include many pregnant women and infants, severely disabled adults and people battling addiction, and many elderly nursing home residents.

The GOP legislation translated to hundreds of billions of dollars in cuts in projected federal payments to states.

"That joined a number of moderate Republicans to the interests of Democrats in not cutting or curtailing Medicaid in a dramatic way," explained economist Gail Wilensky, a Republican. "I think what happened is there was a big overreach."

The National Association of Medicaid Directors, a group whose current members mainly represent Republican-led states, went on record opposing the Senate bill.

"We operate on bipartisan consensus," said Matt Salo, the group's executive director. "Two-thirds of our members work for Republican governors. What we have here is Republican state executives saying there are fatal flaws."

Sen. John Thune, R-S.D., who ranks third in the leadership, says Republicans are not going to give up on repealing "Obamacare."

"It has proven to be quite challenging to get 50 Republicans on board with one solution," he said. "We just haven't gotten there yet."

In his floor speech, McCain offered a possible way forward. He called it "regular order," the plodding work of legislating by committee.

"What have we to lose by trying to work together to find those solutions?" he asked. "We're not getting much done apart."

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EDITOR'S NOTE — Ricardo Alonso-Zaldivar covers health care for The Associated Press.