Still, she did earlier criticize Chief Justice John G. Roberts Jr. for voting to uphold the Affordable Care Act, and she once signed onto an ad calling for overturning Roe v. Wade and its “barbaric legacy.” It is a good bet that she will be among the court’s most conservative justices, probably to the right of Chief Justice Roberts and Justice Brett M. Kavanaugh.
Like five other justices, Judge Barrett is Catholic; she has said her faith is central to her identity. But in other ways, she breaks the court’s mold. A Notre Dame alumna, she will be the only justice who did not graduate from Harvard or Yale. She is also raising seven children, two of whom were adopted.
After playing down its implications during the hearings, some Republicans openly celebrated her anti-abortion rights stance on Monday.
“The nomination of Amy Coney Barrett is truly historic,” said Senator Josh Hawley, Republican of Missouri. “This is the most openly pro-life judicial nominee to the Supreme Court in my lifetime. This is an individual who has been open in her criticism of that illegitimate decision, Roe v. Wade.”
By the time senators gathered on Monday night for the final vote, many were exhausted from a debate that had lasted through Sunday night into Monday and from jetting back and forth between Washington and the campaign trail.
But after Senator Charles E. Grassley of Iowa, the president pro tempore, read the tally, Republicans leaped up from their desks and applauded. Only two did not join them.
One was Ms. Collins, who had left the chamber as soon as she cast a “no” vote. She had framed her decision this time as a matter of principle. Republicans set a standard in 2016 by not confirming a nominee in an election year and should do the same now, she argued. She is trailing in a race in a liberal-leaning state in part because of her constituents’ fury at her vote for Justice Kavanaugh, Mr. Trump’s last nominee.
The other was Senator Lisa Murkowski of Alaska, another Republican swing vote, who sat stone-faced. She ultimately voted to confirm Judge Barrett, but said she feared the hit the court and the Senate would take with the public for proceeding as voters cast their ballots.
Adam Liptak and Emily Cochrane contributed reporting.