Sen Susan Collins
© Aaron Bernstein / ReutersSenator Susan Collins
The Republican's last-ditch effort to repeal and replace the Affordable Care Act, also known as Obamacare, will most likely fail after Senator Susan Collins (R-Maine) became the third GOP senator to come out against the bill.

On Monday, Collins announced she would oppose the healthcare bill sponsored by Senators Lindsey Graham (R-South Carolina) and Bill Cassidy (R-Louisiana), despite the amendments intended to win over her support. Senator Rand Paul (R-Kentucky) announced earlier he would not vote for the bill, which he said "does not repeal ObamaCare." Senator John McCain (R-Arizona) also said he could not support the bill "in good conscience."

Republicans currently hold 52 out of 100 Senate seats, and could get Vice President Mike Pence to break a tie. That means the bill cannot pass with more than two GOP senators voting against it. At least one senator would need to change their mind in order for the bill to pass by September 30, the last day that Republicans could attempt to pass the bill through the budget reconciliation process in the current fiscal year.

Collins said there were three major reasons she opposed the legislation. First, she said the bill would make "devastating" cuts to the Medicaid program, projected to be around $1 trillion over the next decade. "This would have a devastating impact to a program that has been on the books for 50 years and provides healthcare to our most vulnerable citizens, including disabled children and low-income seniors," Collins said.

The senator from Maine also said the bill would allow states to raise premiums for individuals with pre-existing conditions, "potentially making their insurance unaffordable." Finally, she said that the legislation would lead to higher premiums and reduced coverage "for tens of millions of Americans."

Although the most recent version of the bill was written to include additional money for her home state, Collins said that her constituents would suffer in the long-term.

Collins cited the nonpartisan Congressional Budget Office (CBO), which released a preliminary report on a previous version of the Graham-Cassidy bill on Monday. The CBO found the bill would reduce the on-budget deficit by at least $133 billion over the 2016-2017 period. This would suggest the bill meets the requirements under the reconciliation process that allows the Senate to pass the bill with a simple majority.

However, the agency said there was not enough time to provide a specific estimate on how many Americans could lose their insurance under the new legislation, only that the "number of people with comprehensive health insurance that covers high-cost medical events would be reduced by millions."

The agency said they would need "at least several weeks to provide point estimates of the effects on the deficit, health insurance coverage, and premiums," but added that "the direction of the effects is clear."

The CBO report said the number of insured Americans would decrease under the bill, citing the reductions in federal funding for the Medicaid program, the reduction in subsidies, and repealing of penalties for not having insurance.