WASHINGTON — Within a divided Senate Republican caucus, resistance to the party's high-stakes health bill has come from Ohio, West Virginia, Maine, and Nevada – states, like Pennsylvania, that have expanded Medicaid to hundreds of thousands of people and seen the grim opioid epidemic up close.

And yet Pennsylvania's Pat Toomey has been one of the bill's most vocal advocates.

While GOP senators from those other states have decried spending cuts that they say could cost their constituents health coverage and undermine substance-abuse treatment, Toomey has argued that there are no cuts at all in the bill — and has authored a plan to scale back Medicaid even more.

In doing so, Toomey has been one of the most vocal and visible advocates for a controversial bill that could affect health care for millions.

He has vouched for the plan repeatedly on national television, including on a sprint through Fox News, Fox Business, MSNBC, and CNBC on Monday. He touted it in a USA Today column and defended the proposal last week in a question-and-answer session televised on several Pennsylvania stations.

His critics accuse Toomey of putting conservative ideology ahead of Pennsylvania's interests, and of threatening health care for hundreds of thousands of constituents.

The senator rejects those predictions and has defended the bill by standing on the themes that have driven much of his public career: a smaller, leaner government.

"There is no credible person who has looked at our federal financing and come to a conclusion other than that we are absolutely guaranteed to have a full-blown fiscal crisis if we continue on the path that we're on," Toomey said in an interview.

That's why, he argued, it's critical to scale back spending on Medicaid, which covers more than 70 million poor and disabled adults and children, and is one of the most expensive federal programs.

"What we've got is a chance to take a significant step in avoiding that catastrophe by putting one of the biggest drivers of our fiscal imbalance on a sustainable path," he said.

Toomey has also said the GOP bill would help Pennsylvanians by tackling the rising premiums and diminishing choices under the Affordable Cart Act.

But as Republicans have tried to salvage a flagging repeal effort, his most forceful arguments in recent days have echoed the budgetary warnings he has sounded for years. His website is full of charts and data showing Medicaid's growth.

"He's always been first and foremost a fiscal hawk," said Christopher Borick, a pollster at Muhlenberg College.

As the head of the conservative Club for Growth, Toomey once steered one of Washington's most fierce advocacy shops for low taxes, less spending, and fewer regulations. As a senator, he has long promoted what he sees as the need to rein in so-called entitlement programs such as Social Security, Medicare, and Medicaid, which account for roughly half of the federal budget.

In 2011, his eye for finance earned Toomey a seat on a high-profile deficit-cutting panel, where he crafted a proposal that included a provision tying spending programs, including Social Security, to lower inflationary growth.

It wasn't adopted, but now Toomey has authored a similar proposal to lower Medicaid's inflationary increases, putting his own stamp on the GOP bill.

His arguments — that he is not cutting the program but slowing its growth, to make it sustainable and avert a fiscal crisis — use nearly identical language as when he pushed his deficit plan.

Toomey has long made such arguments in pressing for tax and spending policy that he says will spur economic growth. He vociferously opposed Obamacare, and blames it for higher premiums and fewer choices.

During his narrow reelection win last year, Toomey highlighted other topics. He flexed his muscles on national security and promoted himself as a consensus-seeker on issues like gun control.

And he enlisted one of the Senate's most well-known centrists, Maine's Susan Collins, to bolster his moderate credentials.

Now, she is one of the sharpest GOP critics of the Republican health bill. She said Monday it would deal "a devastating blow" to rural hospitals and spike job losses — countering Toomey's dismissal of those concerns just hours earlier in a TV interview.

The differences illustrate the fissures cleaving Republicans. About 10 GOP senators have announced their opposition to the initial bill Toomey helped write. With Democrats uniformly opposed, Republicans can afford only two defections.

Leaders are huddling this week to try to develop a revised version and bring it to a vote as soon as next week.

One change, urged by moderates, would leave in place some ACA taxes on people with high incomes — an idea Toomey opposes but said was not a deal-breaker.

Most Republicans appear ready to support the Senate bill. And Toomey is not the most conservative voice on the issue: Some opponents, such as Texas' Ted Cruz and Utah's Mike Lee, want the GOP bill to go further in ripping up the ACA.

But his state has more in common with the likes of Rust Belt neighbors Ohio and West Virginia, whose Republican senators have been critics of the plan.

Medicaid's expansion has provided health coverage to more than 700,000 Pennsylvanians, Gov. Wolf has stressed, more than 124,000 of whom received treatment for drug or alcohol addiction as the state copes with an opioid crisis.

"How could any Republican senator vote to destroy the Affordable Care Act when it has helped so many of their constituents?" Sen. Bernie Sanders (Ind., Vt.) wrote on Twitter recently.

Nationwide, 22 million fewer people are expected to have health insurance by 2026 under Senate Republicans' original plan, the nonpartisan Congressional Budget Office estimated, compared with current law. Some of the largest reductions would hit Pennsylvania, according to the Urban Institute, a think tank. That's due in large part to what the CBO projects as a $772 billion cut in projected Medicaid spending, though Toomey has sharply disputed its methodology and predictions.

Pennsylvania would lose $4.5 billion in annual Medicaid funding once all the GOP changes take effect, in 2025, according to Wolf's office. In a state where officials already struggle to pass budgets, future administrations would have to either come up with those extra dollars or cut services.

"In our state, everywhere I look there's an adverse impact when it comes to Medicaid," said Pennsylvania's other senator, Democrat Bob Casey.

Toomey has focused on other numbers: a nearly $700 billion federal deficit and $385 billion spent on Medicaid. It's expected to grow to more than $655 billion by 2027, far outpacing the economy.

Tellingly, while the bill's opponents have targeted several swing-state Republicans, national advocacy groups working against it have not tried to pressure Toomey, who has the political cushion of a fresh six-year term.

Conservative columnist George Will hailed Toomey's proposal — tying Medicaid to a lower measure of inflation — as potentially "this century's most significant domestic policy reform." The highly technical shift would save the federal government, and cost states, billions over time.

It's one of several changes to Medicaid that Republicans are proposing and that Toomey expects to remain in the new bill — despite the internal objections.

Toomey argues that coverage won't be affected if states come up with their "fair share" of funding. Democrats say it's unrealistic to expect governors to find billions of dollars in new money.

Some Republicans have made the same point.

When Sen. Dean Heller (R., Nev.) questioned whether the 200,000 people in his state who gained Medicaid coverage would keep it in the GOP plan, he provided his own answer: "I'm telling you right now, it doesn't do that."