âShe is unshakable when it comes to her constituents,â said Senator Susan Collins, Republican of Maine, the other Republican who opposed Tuesdayâs procedural vote. âShe has a spine of steel.â
Given the narrow 52-48 party divide in the Senate and the shrinking ranks of more moderate congressional Republicans, Ms. Murkowski has emerged as a key swing vote, giving her new influence. Nowhere has that been on display as much as in the health care fight.
Senator Mitch McConnell, the Kentucky Republican and majority leader, shaped his health care proposal with an eye toward Alaska, adding billions of dollars to help hold down insurance premium costs in a state where health care choices are very limited, as well as extra money for the care of native populations. Those provisions were added not only to woo Ms. Murkowski, but also to secure the vote of Dan Sullivan, the other senator from Alaska and a fellow Republican.
Ms. Murkowski remained leery of the health care proposal, expressing concern about its potential effects on the many Alaskans who rely on Medicaid, as well as the partisan manner in which it was being assembled behind closed doors by Republican leaders. Before the vote on Tuesday, she informed her colleagues she would break ranks.
âIâm very comfortable with the decision I made yesterday in working to advance Alaskaâs interests,â Ms. Murkowski told reporters on Wednesday, adding that she doesnât âreally follow Twitter.â
Mr. Trump wasnât the only irritated Republican. Representative Blake Farenthold, Republican of Texas, suggested that he might challenge the Senate Republican women opposing repeal to a duel, and a second House Republican, Representative Earl L. Carter of Georgia, on Wednesday issued a vulgar but incomprehensible insult.
Ms. Murkowski has already challenged Mr. Trump this year. She and Ms. Collins were the only two Republicans to oppose Betsy DeVos, Mr. Trumpâs choice for education secretary, with Ms. Murkowski citing the nomineeâs lack of experience in public education.
Ms. Collins said that as she and Ms. Murkowski, whose Senate desks are adjoining, prepared to turn their thumbs down on Tuesday, they discussed the possibility that the leadership might want to change their seating arrangement to keep them from being bad influences on each other.
Despite her position on the health care bill and her support for abortion rights, Ms. Murkowski remains a reliably Republican vote on most issues. An avid outdoorswoman, she draws regular criticism from Democrats and environmental activists for her support of the oil and gas industry â mainstays in her state â and the conservative stance she takes on other issues involving public lands and wildlife.
But in this case, Democrats credit her for a position they acknowledge must be difficult to maintain.
âIâm very impressed by what she is doing to try to get the right decision made,â said Senator Maria Cantwell of Washington, the senior Democrat on the Energy and Natural Resources Committee. âWhat she is trying to do is figure out how to preserve something that is so vital up there in her state.â
Ms. Cantwell, who has negotiated a bipartisan energy measure with Ms. Murkowski that could soon be acted on by the Senate, has traveled with her in Alaska. She said she had witnessed firsthand how truckers and fishermen have urged their senator to do what she could to maintain the health coverage they now rely on.
Ms. Murkowskiâs vote on Tuesday made her the only Senate Republican who supported the repeal bill passed in 2015 to oppose moving ahead with the debate. She said circumstances in her state had changed significantly in the past two years.
Ms. Murkowski, who has little to no interest in national news coverage, carries a famous Alaskan name that has been an advantage and a hindrance. Her father, Frank Murkowski, was a four-term senator who left Congress in 2002 to run successfully for governor. After he was elected, he appointed his daughter Lisa, a state lawmaker, to his Senate post. Accusations of nepotism dogged her in her first campaign, in 2004, but she won â only to lose the Republican primary to Joe Miller, a Tea Party firebrand, six years later.
That 2010 defeat led national and state Republicans to pull support from her and caused some tension with her Senate colleagues, some of whom suggested she should be stripped of committee seniority. But her ultimate victory in the general election and the 2014 Republican takeover of the Senate seemed to smooth over any hard feelings. She has what is considered a decent working relationship with Mr. McConnell, though some colleagues occasionally bristle at her breakaway nature.
After Republicans met on Wednesday to plot their next move, Ms. Murkowski said she hoped the Senate could still find its way to a health care proposal she could support.
âI think there are areas we can identify that we can find common ground,â she said. âThat is kind of the hope and desire, and Iâm simply willing to start to find how we can get to that point.â
The limits of Ms. Murkowskiâs independence may still be tested.