Here's why the GOP health reform bill collapsed

• The GOP health reform bill got stuck between a rock and a hard place.
• The rock was a group of conservative senators who thought the compromise bill didn't go far enough to wipe out the Affordable Care Act.
• But moderate Republicans found themselves in the hard place of explaining the bill to millions of voters who would see coverage evaporate or insurance premiums soar.

The GOP health reform bill ultimately failed because it got stuck between a rock and a hard place.

The rock — in the form of conservative senators including Rand Paul of Kentucky, Mike Lee of Utah and Jerry Moran of Kansas — represented the view that the compromise bill didn't go far enough to wipe out the Affordable Care Act that provided health coverage to tens of millions of Americans.

"The current system is terrible," Paul told Fox News on Sunday. "I don't think Republicans should put their name on this (bill)."

But moderate Republicans — including Susan Collins of Maine and a handful of other "undecided" GOP senators — found themselves in a hard place facing the millions of voters who would see coverage evaporate or insurance premiums soar, according to multiple analyses of the bill's impact.

Many of those voters are among the 70 million recipients of Medicaid, the federally subsidized, state-administered program that was expanded under Obamacare. The bill, known as the Better Care Reconciliation Act, would have reversed that expansion over three years, from 2021 to 2024, and then make deeper cuts in 2025.

"We should not be making fundamental changes in a vital safety-net program that's been on the books for 50 years — the Medicaid program — without having a single hearing to evaluate what the consequences are going to be," Collins said.

The latest version of the bill collapsed late Monday when Lee and Moran joined Collins and Paul in promising to vote "no." Those defections doomed the measure in the Senate, where Republicans enjoy a slim 52-48 margin. Democrats remain unified in their opposition to the GOP reform measure.

The demise of the act left President Donald Trump fuming and GOP leadership scrambling to find a new strategy to show progress on an issue that was one of the party's signature campaign issues in the 2016 election. Senate Majority Leader Mitch McConnell of Kentucky was reported to be maneuvering to call a vote on a full repeal of Obamacare, effectively starting over on a compromise plan to replace the nation's public health insurance system.

That would leave moderates like Collins still stuck in the hard place of facing voters worried about losing coverage. Though Maine is not among the 32 states that chose to expand Medicaid coverage under Obamacare, it is one of the country's most rural states, which tend to have older populations and higher health care costs, according to the Center for Budget Policies and Priorities.

Other holdouts — who maintained they were "undecided" in advance of the vote — include a handful of senators from states that expanded Medicaid and stand to lose the most in federal funding if the latest draft of the bill is approved.

Those include Republican Sen. Dean Heller of Nevada, who won his seat by a slim margin and faces a tough re-election in 2018. Heller was among the five GOP senators to publicly oppose the original version of the Senate bill last month. A majority of Nevada voters oppose the bill, according to recent polls, and it was opposed by Nevada's Republican governor, Brian Sandoval.

Moderate GOP Republicans also balked after several analyses found that the replacement plan would create big increases in premiums for older health insurance customers and those with chronic illnesses. Some younger, healthier consumers would have seen lower premiums for plans that offered minimum levels of coverage.

The failed bill also promised big Medicaid cuts for Alaska, North Dakota and West Virginia, rural states with high per capita health-care costs. That put Alaska Sen. Lisa Murkowski, North Dakota Sen. John Hoeven and West Virginia Shelley Moore Capito on the "undecided" list.

Fresh from one of the toughest rounds of annual state budget battles since the Great Recession, Republican governors had also worried that big federal Medicaid cuts under the doomed replacement bill would leave them with big revenue shortfalls at a time when many states are scrambling to balance their budgets.

Those include Republican Gov. John Kasich of Ohio, which would have lost some $13 billion in Medicaid funding through 2026, according to an analysis by Avalere, a health-care consulting firm.

That funding shortfall and possible coverage cuts left Ohio Sen. Rob Portman, who won his seat comfortably in 2016, in the "undecided" column on the replacement bill.

Now, as the GOP tries to repeal Obamacare with no replacement in place, Portman and others with concerns about cuts in funding and coverage will be even harder to win over.

"We have to look and see what the so-called repeal bill entails," he told reporters Tuesday. "But if it is a bill that simply repeals, I believe that will add to more uncertainty and the potential for Ohioans to pay even higher premiums and higher deductibles. So, we'll have to see."

WATCH: Trump says elect more Republicans to change health care