WASHINGTON — The GOP's last-ditch effort to repeal and replace Obamacare received what appeared to be a fatal blow Monday evening when Sen. Susan Collins, R-Maine, announced her decision not to support the bill, becoming the crucial third Republican to oppose it.

Collins joins Sens. John McCain of Arizona and Rand Paul of Kentucky as GOP "no" votes. Unless one of them switches their position, Republicans can't muster the 50 voted needed to pass it.

Gallery: Capitol Hill Protests Interrupt GOP Health Care Bill Hearing

Momentum for the bill sputtered Monday morning even after a new version was released by authors Sens. Lindsey Graham of South Carolina and Bill Cassidy of Louisiana that included new incentives to appease the concerns of a handful of uncommitted Republican senators.

GOP leaders faced a Saturday deadline to pass Graham-Cassidy with a simple Senate majority, and it's still unclear if they will put the bill up for a vote without the votes for it to pass.

Leaving a leadership meeting, Sen. Orrin Hatch, R-Utah, said, "I doubt it" when asked if Senate Majority Leader Mitch McConnell would bring the legislation to the floor for a vote. And that was before Collins had solidified her position against it.

Collins' opposition caps off a months-long effort to repeal the Affordable Care Act after years of campaign promises to do so. Senate Republicans failed to pass three other versions of a repeal to Obamacare in late July when Collins, McCain and Sen. Lisa Murkowski, R-Alaska, all voted against it.

Murkowski has not yet indicated her position on Graham-Cassidy.

"Today, we find out that there is now a fourth version of the Graham-Cassidy proposal, which is as deeply flawed as the previous iterations," Collins said in a statement announcing her opposition. "The fact that a new version of this bill was released the very week we are supposed to vote compounds the problem."

Collins announced her position despite last-minute changes to the bill to get remaining holdouts on board. An analysis of state-by-state health care funding shows that under Graham-Cassidy, Maine would see a 43 percent increase in federal health care funds, Arizona would get an additional 14 percent, Kentucky 4 percent and Alaska 3 percent.

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But Collins said that despite the positive numbers, "Maine still loses money under whichever version of the Graham-Cassidy bill we consider because the bills use what could be described as a 'give with one hand, take with the other' distribution model."

"Huge Medicaid cuts down the road more than offset any short-term influx of money," she said.

Collins announced her position after an incomplete analysis of an earlier version of Graham-Cassidy by the Congressional Budget Office found that "millions" would lose their health insurance under the plan.

The rushed process to meet a Saturday deadline for allowing passage with just a simple majority frustrated a handful of senators, including McCain who had more problems with the process than with the substance. He came out against the bill on Friday.

In an effort to calm the critics on process, the Senate Finance Committee held the first and only hearing Monday afternoon on the legislation. It turned out to be highly attended by passionate activists worried about their health care being stripped from them.

Protestors filled the hallways outside the hearing room, snaking around the corner and down the length of a city block. Hundreds of people chanted "shame" as Graham entered to testify before the committee. Voluminous protests inside the hearing room delayed the start of the hearing. Hatch, the committee's chairman, tried to gavel in the committee but protestors drowned him out. Police dragged them out, many disabled and in wheelchairs, one by one. The Capitol Police said Monday night that 181 protestors had been arrested at the demonstration.

Chairman Hatch is trying to gavel in. I don't see how this hearing ever starts. Activists are passionate and determined pic.twitter.com/mBEdIWoCOB — Leigh Ann Caldwell (@LACaldwellDC) September 25, 2017

Once the hearing began, protestors maintained their chants in the hallway outside, their voices seeping through the doors. The Association of Health Insurance Plans and Blue Cross Blue Shield released prepared testimony before the hearing stating that they can't support Graham-Cassidy.

"The bill would have negative consequences on consumers and patients by further destabilizing the individual market; cutting Medicaid; pulling back on protections for pre-existing conditions; not ending taxes on health insurance premiums and benefits; and potentially allowing government-controlled, single-payer health care to grow," a summary of their testimony states.

Graham testified that Obamacare was a “disaster” in his state and boasted that "every major insurance company opposes our bill,” saying it was evidence that his legislation would give states more flexibility in dealing with them.

But Democrats pointed out it wasn’t just insurers upset with Graham-Cassidy: The top industry groups representing doctors and hospitals also publicly opposed the bill along with a parade of patient advocacy groups, from AARP to the American Heart Association. These organizations have argued the bill would cut overall health funding while allowing insurers to treat customers differently based on a pre-existing condition, a practice banned by Obamacare.

Under questioning from Senator Ron Wyden, D-Ore., Cassidy said their assessments were wrong and that it was “not true” that states could charge higher premiums based on their health status under his bill.

But the bill as written allows states to waive Obamacare’s rule preventing insurers from charging sick people more for care as well as its requirements that plans cover certain essential benefits. Outside analysts have consistently said it would weaken protections for pre-existing conditions.

The loosening of the regulations on insurance coverage was seen as an attempt to help conservatives come on board.

Protestors also sat-in the office of Murkowski in protest. Her deputy chief-of-staff came out to address the activists and said that she left Anchorage at 6 a.m. on Monday and was using her flight time to Washington “thinking about her decision.”

Marilee Adanski-Smith came from Wisconsin on Saturday to attend the hearing. She was born without arms and legs and relies on Medicaid.

“We’re here to save Medicaid. Our lives depend on Medicaid,” she said, adding that she’s fearful that the legislation will take away Medicaid recipients' ability to live at home and force people into nursing homes.

“People are going to die in nursing homes if people don’t have the community and home-based services they need,” Adanski-Smith, a small-business owner, added.

Marilee Adamski-Smith from Brookfield, Wisconsin, left, and Colleen Flanagan of Boston, center, join others outside a hearing room where the Senate Finance Committee will hold a hearing to consider the Graham-Cassidy healthcare proposal, on Capitol Hill in Washington on Sept. 25, 2017. Manuel Balce Ceneta / AP

Graham-Cassidy would end the Medicaid expansion in 2020 and reduce the money given to Medicaid by changing how it's allocated. It would no longer provide it for whoever is in need — instead, it would cap the number based on population.

The bill would also end the individual mandate to buy insurance and dismantle the structure of the Affordable Care Act, widely known as Obamacare. Instead, it would give money to states to implement their own health care systems. And while it would require that people with pre-existing conditions have access to health insurance, like Obamacare, it wouldn't prohibit insurance companies from charging people with long-term health care needs more money.

The new version of Graham-Cassidy would also provide billions of dollars more for states during the transition from Obamacare and as a contingency fund.