WASHINGTON — Lisa Murkowski had heard enough.
As President Donald Trump pressed her and her fellow Senate Republicans recently to fall in line behind a repeal of the Affordable Care Act in the interest of party loyalty and protecting the Republican brand, she felt compelled to speak up.
"With all due respect, Mr. President," she said, according to some of the people at the private White House lunch, "I didn't come here to represent the Republican Party. I am representing my constituents and the state of Alaska."
Trump did not appreciate the pushback. After Murkowski was one of just two members of her party to oppose a critical procedural vote Tuesday, Trump voiced his displeasure on Twitter: "Senator @lisamurkowski of the Great State of Alaska really let the Republicans, and our country, down yesterday," he wrote Wednesday morning. "Too bad!"
But it may be that it's too bad for Trump, because he picked on someone unlikely to be rattled by his attack or by accusations that she deserted her fellow Republicans. Murkowski already survived a political near-death experience in 2010 when she lost a primary race to a tea party challenger and was essentially abandoned by the Republican Party.
She won a stunning victory in a rare write-in campaign — and "Murkowski" is not all that easy to write in — returning to Washington still a Republican but one with a well-defined independent streak and a reputation of fierce advocacy for her remote and sometimes overlooked state.
"She is unshakable when it comes to her constituents," said Sen. Susan Collins, R-Maine, the other Republican who opposed Tuesday's procedural vote. "She has a spine of steel."
Given the narrow 52-48 party divide in the Senate and the shrinking ranks of more moderate congressional Republicans, 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.
Sen. Mitch McConnell, R-Ky., the 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 Murkowski but also to secure the vote of Dan Sullivan, the other senator from Alaska and a fellow Republican.
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 Tuesday, she informed her colleagues she would break ranks.
"I'm very comfortable with the decision I made yesterday in working to advance Alaska's interests," Murkowski told reporters Wednesday, adding that she doesn't "really follow Twitter."
Trump wasn't the only irritated Republican. Rep. Blake Farenthold, R-Texas, suggested that he might challenge the Senate Republican women opposing repeal to a duel, and a second House Republican, Rep. Earl L. Carter of Georgia, on Wednesday issued a vulgar but incomprehensible insult.
Murkowski has already challenged Trump this year. She and Collins were the only two Republicans to oppose Betsy DeVos, Trump's choice for education secretary, with Murkowski citing the nominee's lack of experience in public education.
Collins said that as she and Murkowski, whose Senate desks are adjoining, prepared to turn their thumbs down 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, 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 — mainstays in her state — 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.
"I'm very impressed by what she is doing to try to get the right decision made," said Sen. Maria Cantwell of Washington, the senior Democrat on the Energy and Natural Resources Committee. "What she is trying to do is figure out how to preserve something that is so vital up there in her state."
Cantwell, who has negotiated a bipartisan energy measure with 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.
Murkowski's vote 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.
Murkowski, who has little to no interest in national news coverage, carries a famous Alaska 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 — 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 McConnell, though some colleagues occasionally bristle at her breakaway nature.
After Republicans met Wednesday to plot their next move, Murkowski said she hoped the Senate could still find its way to a health care proposal she could support.
"I think there are areas we can identify that we can find common ground," she said. "That is kind of the hope and desire, and I'm simply willing to start to find how we can get to that point."
The limits of Murkowski's independence may still be tested.
Carl Hulse is chief Washington correspondent for The New York Times.