On Monday, 237 organization sent a letter to the Senate opposing Republicans' latest attempt to repeal key components of the Affordable Care Act and take away basic healthcare from millions of Americans.
Collins, who hails from ME, announced her decision shortly after the nonpartisan Congressional Budget Office projected the bill would cut Medicaid benefits by $1 trillion through 2026. Lindsey Graham of SC and Bill Cassidy of Louisiana, would eliminate the mandate that everyone has to have health insurance.
Republicans can afford to lose the votes of just two of their 52 GOP senators to pass the bill.
"I can not support the bill", Collins told reporters Monday night, adding that President Donald Trump and senior members of his administration had tried to woo her over the weekend.
The bill's sponsors and Senate Majority Leader Mitch McConnell, R-Ky., are facing an imminent deadline because special budget rules that would allow the chamber to pass the bill with a simply majority - and no Demcratic votes - ends on Saturday.
The CBO said that fewer people would be covered because subsidies that help people pay premiums and other financial aid would be eliminated, and individuals would no longer be required to have insurance or pay a fine. "However it was clear to me that the Graham-Cassidy bill was not the answer", Collins told ABC News.
Both Graham and Cassidy appeared in front of the Senate Finance Committee Monday as part of the only committee hearing into the bill now scheduled.
Numerous Democratic critics of the proposal, along with several major health care groups in the country, say that over the coming years the change in the law would cut millions of people from insurance rolls.
Collins announcement makes it nearly impossible for senators to reach that threshold, unless they can persuade either Sen.
Paul criticized as "unseemly" Graham's and Cassidy's latest effort to tweak their legislation to sweeten the deal for states like Alaska, Arizona and ME in order to lure skeptical senators from those states. If all three Republicans maintain their opposition, the bill will be dead.
Graham suggested Republicans could have another shot at repealing Obamacare, even if they do not do it this week, if Senate leadership were to attach a repeal bill to a planned tax reform package.
Paul told reporters after an event in his home state he still plans to vote against the Republican bill that would repeal former President Barack Obama's health care law. None of their concerns could be easily fixed by changing funding formulas.
Senator Susan Collins, who has waffled for weeks on the latest measure that would overhaul Obamacare, joined Republican colleagues John McCain and Rand Paul as firm no votes on the legislation. The bill also added a provision that would give Hawaii and Alaska more money for traditional Medicaid matches; Alaska Sen.
Other Republicans are wavering, too. Lindsey Graham (R-SC) and Bill Cassidy (R-LA) released a new draft Monday.
President Donald Trump made repealing Obamacare one of his top campaign promises in 2016.
Cruz says he doesn't think Utah GOP Sen.
"I am so sorry about this process, I would prefer hearings, a markup and Democrat co-sponsors", Cassidy said at the beginning of his testimony in response to Wyden, who had attacked Republicans for their process in his opening remarks.