Of the more than 10,000 votes cast by Senator Susan Collins of Maine, there is one that has shadowed her like no other as she runs for a sixth term.

On Oct. 6, 2018, Ms. Collins, one of only two Senate Republicans who support abortion rights, cast a deciding vote to confirm Brett M. Kavanaugh to the U.S. Supreme Court. Four years later, Justice Kavanaugh voted with the conservative majority to overturn Roe v. Wade, which had guaranteed a constitutional right to abortion for nearly half a century.

The vote cut against her well-cultivated reputation as a moderate Republican who is unafraid to break ranks. It also put her at odds with abortion rights activists, who had previously backed her campaigns, and with advocates for victims of sexual violence, who rallied behind a woman who accused Mr. Kavanaugh of sexual assault, an allegation he denied.

Now, Ms. Collins’s support for Justice Kavanaugh has become a major issue in her first re-election campaign since Roe was overturned, a race that could swing control of the Senate. The 2018 vote has emerged as a character test of Ms. Collins for Maine voters: Some consider her a principled lawmaker taking tough votes, while others see a calculating politician determined to keep her job.

Publicly, Ms. Collins appears unbowed. “I do not regret that vote,” she told reporters in Portland in June. She went even further after an event at a fire station in Randolph, Maine, this month.

“I would vote for him again, yes,” she said, according to audio acquired by an operative for American Bridge, a major Democratic super PAC.

But people who interacted with her during the Kavanaugh hearings say Ms. Collins still harbors frustrations about the continued backlash after a confirmation process she described in 2018 as “more like a caricature of a gutter-level political campaign.”

Even as she was accused of capitulating to the demands of her party and President Trump, Ms. Collins believed she took the more politically difficult vote while representing a Democratic-leaning state, she told a confidant at the time. And in the years since, she has appeared to hold grudges against people who criticized her vote.

“She takes all of it very personally,” said Dana Singiser, a former Planned Parenthood vice president, who raised concerns about Judge Kavanaugh with Ms. Collins during his confirmation process. “For us, it’s not really personal, it’s just about our mission. That was an abortion-defining vote.”

This account is based on interviews with more than two dozen former aides, Senate colleagues, activists and others involved in the confirmation process. Some spoke on the condition of anonymity to discuss private conversations.

Ms. Collins declined an interview request from The New York Times. Blake Kernen, a spokeswoman for Ms. Collins, dismissed criticism of the senator’s vote as driven by “hyperpartisan voices.”

“Senator Collins fully and honestly explained her decision in the days before and the years that followed Justice Kavanaugh’s nomination,” she said.

Ms. Kernen also drew a contrast between the senator, who she said “has always been pro-choice,” and her Democratic opponent, Troy Jackson, who opposed abortion as a state lawmaker until about a decade ago. He later helped enact a Maine law that allows abortion at any stage of pregnancy, as long as a doctor deems it necessary — one of the most permissive in the country.

Ms. Collins’s allies say she made a principled decision to back Judge Kavanaugh after extensive research, including hours of conversations with him, scrutiny of his work and feedback from thousands of constituents. In the end, they say, her vote came down to a simple calculation: She believed Judge Kavanaugh when he said he would respect precedent, which she interpreted to mean that he would leave Roe v. Wade largely intact. And she did not believe Christine Blasey Ford, the California professor who said he sexually assaulted her when they were in high school.

“She did her job,” said Mike Davis, who helped spearhead Justice Kavanaugh’s confirmation as chief nominations counsel for the Senate Judiciary Committee’s chairman. “She did her homework.”

But what she saw as a conscientious vote provoked years of protests from Capitol Hill to her home in Maine. As the years progressed, she grew irritated by liberals continuing to vilify her support for Justice Kavanaugh while failing to acknowledge her support for the three justices nominated by Democratic presidents, Sonia Sotomayor, Elena Kagan and Ketanji Brown Jackson.

“It is a major source of frustration for Senator Collins that while there seems to be an endless discussion of the Kavanaugh confirmation, there is never any mention that she is the only Republican senator to have voted to confirm all three,” said Stephen Diamond, a Maine attorney who helped her prepare for the Kavanaugh confirmation hearing.

Ms. Kernen defended Ms. Collins’s record on abortion rights, noting that a Maine affiliate of Planned Parenthood commended her in 2025 for opposing Republican efforts to defund the organization. And she pointed to legislation that Ms. Collins introduced in 2022 that she said would codify abortion rights into federal law. But the senator voted against a broader Democratic measure preferred by advocates for abortion rights, saying it was championed by “far-left activists.”

Kay Rand, who served as chief of staff for Senator Angus King, a Maine independent who caucuses with Democrats, said the vote shifted views of Ms. Collins in Maine, even as she handily won re-election in 2020.

“It’s just never been the same for her since the Kavanaugh vote,” said Ms. Rand, who worked for Mr. King during the Kavanaugh hearings. “It was a lightning rod, a galvanizing issue.”

A clear litmus test

Even before President Trump unveiled his pick to replace retiring Justice Anthony Kennedy on the Supreme Court, Ms. Collins issued a clear litmus test: She would not support any judge who demonstrated “hostility” to Roe v. Wade.

With Judge Kavanaugh, who sat on a federal appeals court and had worked in the George W. Bush White House, the Trump administration believed it had found a nominee who could satisfy Ms. Collins, a pivotal swing vote at a time when Republicans held a single-seat majority.

The nomination was announced in July 2018, and Ms. Collins began preparing for a fraught confirmation process. Her approach, she has said, is to defer to the White House on judicial selections as long as the nominees are qualified and within the legal mainstream.

She put together a team of five lawyers to help her learn all she could about the nominee, recalled Mr. Diamond, who had previously served as Ms. Collins’s legislative director and joined the team. The nonpartisan Congressional Research Service offered 10 hours of briefings covering Judge Kavanaugh’s significant opinions, speeches and articles. Ms. Collins attended all the sessions, Mr. Diamond said.

She also had a two-hour meeting in her Capitol Hill office with the nominee himself. When she emerged, Ms. Collins told reporters they had discussed abortion cases “at length,” and that Mr. Kavanaugh said he agreed with Chief Justice John G. Roberts Jr., who said during his 2005 confirmation hearings that he regarded Roe as “settled law.”

Mr. Diamond left the meeting with a similar impression.

“I am pro-choice and I came away with the conclusion that there was a reasonable possibility that he would not overturn Roe, though maybe modify it around the edges,” he said.

Abortion rights advocates viewed the senator’s statements as naïve or willfully ignorant. A year earlier, Judge Kavanaugh had dissented from a high-profile decision that allowed a 17-year-old detainee in an immigration facility to receive an abortion, a notable position given his limited record on the issue. He argued that the decision created a new right for “immediate abortion on demand,” adopting the political language of the anti-abortion movement.

The day after her meeting with Judge Kavanaugh, Ms. Collins reassured Julia McDonald, a Maine physician who performed abortions, that she had asked the nominee “hard questions” about his view of Roe and she believed his commitment to stare decisis, the legal doctrine that directs courts to follow precedent-setting cases.

“Those of us in that meeting pushed back hard, asking how she could believe that from a man with his record,” said Dr. McDonald, who met with Ms. Collins in her office alongside two patients, another doctor and a Planned Parenthood representative. “She was not interested in hearing our concerns. It seemed very clear that she had made up her mind.”

At times, Ms. Collins seemed focused on smaller issues. In two meetings with Planned Parenthood leaders, she complained that Colby College students had distracted from her May commencement address — before Judge Kavanaugh was even nominated — by wearing “I stand with Planned Parenthood” stickers, according to people present in the meetings.

The activists were taken aback by the senator’s remarks, given the stakes of the confirmation fight. To the Planned Parenthood leaders, the stickers were not antagonistic: Less than a year earlier, the organization had honored Ms. Collins.

Escalating pressure

By early September 2018, Ms. Collins was feeling the brunt of the escalating pressure on the few undecided senators. Agitated and sometimes crude callers besieged her offices. About 3,000 coat hangers arrived by mail, stark reminders of the time before Roe. v. Wade, when desperate women used hangers to try to end unwanted pregnancies. Protesters stood outside her home, wearing red robes and white bonnets like the characters in Margaret Atwood’s dystopian novel, “The Handmaid’s Tale.”

There were also violent threats, including a fax from someone promising to slit her throat and sever her limbs if she voted for Judge Kavanaugh. One man ambushed her outside her home in Washington in the rain after she arrived from work late at night.

The Trump administration was mounting its own pressure campaign. Mr. Davis, a lawyer for the Senate Judiciary Committee, recalled warning Ms. Collins about one scenario that he said did give her pause: Judge Amy Coney Barrett, who had been promoted by abortion opponents, was likely next on the president’s shortlist.

“Judge Kavanaugh was seen as our best hope of preserving Roe,” Mr. Diamond, the former Collins staffer, said.

Then on Sept. 16, the confirmation process took a dramatic turn. . The Washington Post reported that Dr. Ford had accused Judge Kavanaugh of pinning her down on a bed, groping her, and attempting to pull off her bathing suit at a high school party in the 1980s. She said he covered her mouth with his hand to muffle her screams.

Judge Kavanaugh denied what he called “false accusations.”

Ms. Collins immediately pushed for both Dr. Ford and Justice Kavanaugh to testify under oath. She told reporters she was “appalled” when the president attempted to undermine Dr. Ford on social media.

Hours after Dr. Ford’s testimony, Tamara Field, a freelance journalist from Camden, Maine, traveled with about 20 other women on an overnight bus to Washington, D.C., hoping to urge Ms. Collins in person to reject the nomination.

Sitting in Ms. Collins’s office, Ms. Field recounted being sexually assaulted on a first date just a few months earlier. Ms. Collins hugged her and thanked her for sharing her story, she said, but Ms. Field felt in her gut that the senator was leaning toward supporting Judge Kavanaugh.

Years later, she still feels betrayed.

“Susan Collins can look somebody in the eye and tell them how sorry she is that they were attacked and then vote for a man that probably in my opinion committed sexual assault,” Ms. Field said. “There’s a duplicity to her.”

As Judge Kavanaugh’s nomination advanced through the Senate Judiciary Committee, Ms. Collins joined calls from Jeff Flake, then a Republican senator of Arizona, for an F.B.I. investigation of Dr. Ford’s allegations — and a one-week delay in the confirmation process.

Mr. Flake recalled eating dinner with Senator Collins that evening, along with Sen. Lisa Murkowski, a moderate Republican from Alaska. The mood was tense.

“I know the vote was weighing on her,” said Mr. Flake, who described “massive” pressure from both sides of the political spectrum. “There were obviously death threats to me and my family and to her. This was a tough time.”

Ms. Collins continued her research, spending time in the secure room where the F.B.I.’s investigative materials into the case were stored. She contacted friends of the judge to ask if they could imagine him doing anything like this, speaking to former colleagues including former Secretary of State Condoleezza Rice. George W. Bush called twice to lobby her personally.

“She put the Senate judiciary staff through the ringer,” Mr. Davis recalled. “She was in a league of her own in terms of the level of scrutiny and attention to detail.”

A Republican ‘star’

By the time Ms. Collins was ready to announce her decision on Oct. 5, few knew for certain what she would say. Ms. Murkowski, the only other Senate Republican who favored abortion rights, had announced she would vote against Judge Kavanaugh. So had Senator Heidi Heitkamp, a Democrat from the red state of North Dakota. The three women had kept in close contact during the process, discussing the claims, testimony and evidence.

Ms. Collins stepped behind the lectern on the Senate floor and launched into a point-by-point defense of Judge Kavanaugh.

She described the future justice as “more of a centrist.” She was confident he would uphold the Affordable Care Act’s health insurance protections for pre-existing medical conditions and the federal right to an abortion. And she was convinced he would serve as a check on presidential power.

“My fervent hope is that Brett Kavanaugh will work to lessen the divisions in the Supreme Court so that we have far fewer 5-4 decisions and so that public confidence in our judiciary and our highest court is restored,” she said.

Though Ms. Collins described Dr. Ford’s testimony as “sincere, painful and compelling,” the senator said her allegation did not meet a “more likely than not” standard.

Twenty-four hours later, she cast her vote for Justice Kavanaugh.

“I do not believe that Brett Kavanaugh was her assailant,” she said in a CNN interview that aired shortly after the vote. “I do believe that she was assaulted. I don’t know by whom. I’m not certain when.”

Lisa Banks, one of the attorneys who represented Dr. Ford, called the notion that she had misidentified her attacker “preposterous,” in a recent interview. She added, “If Senator Collins had questions or wanted to speak directly with Dr. Ford about her experience and allegations, Dr. Ford would have gladly done so.”

Ms. Collins’s fellow Republicans hailed her as a hero. Mr. Trump praised her effusively and dubbed her a “star.” Leonard Leo, the conservative megadonor credited with helping Mr. Trump build the court’s conservative majority, held a fund-raiser for Ms. Collins at his Maine home the following year.

The event drew picketers, which Ms. Collins called “just ridiculous, absolutely ridiculous,” according to a Bloomberg reporter

Three years later, in the hours after Roe fell, protests exploded across the nation. Ms. Collins felt compelled to defend her decision-making process.

She took the unusual step of releasing private notes from her meeting with Judge Kavanaugh in which he talked about his respect for court precedent. “I feel misled,” Ms. Collins said then. Lance Dutson, a Maine Republican and a former campaign aide to Ms. Collins, said the senator should not be blamed for Justice Kavanaugh’s decision. She did her research, was transparent with her constituents and made the best decision she could at the time, he said.

“She took a Supreme Court nominee’s word,” he said. “From the information she got, she felt comfortable voting for him, and things went the other way after the fact.”

The senator’s unease over criticism of her vote lingered. In a 2021 phone conversation, she confronted a Biden administration nominee who had criticized her support for Judge Kavanaugh on social media. Ms. Collins described those posts as “nasty” and implied that the remarks disqualified the candidate for the position, according to a person familiar with the confirmation process. The nominee was later confirmed, without Ms. Collins’s vote.

The senator’s support for Justice Kavanaugh effectively ended her relationship with Planned Parenthood, the country’s largest provider of reproductive health care. In 2017, the organization had honored Ms. Collins for opposing Republican efforts to cut its funding. Three years later, it endorsed her Democratic opponent.

In 2021, as Ms. Singiser was cleaning out her desk at Planned Parenthood, she discovered an artifact of the old relationship: Posters printed before the Kavanaugh confirmation that read, “I stand with Susan Collins.”

“I thought, ‘If she does something really great we’re going to use them,’” said Ms. Singiser, who now advises reproductive rights organizations. “And then, she never did anything great for us.”