Ms. Collins is among the senators likeliest to face a painful squeeze at the ballot box as a result of Supreme Court politics. In a New York Times poll published on Friday, and conducted before Justice Ginsburg’s death, 55 percent of Maine voters said they disapproved of her vote to confirm Justice Kavanaugh. By a 22-point margin, voters in the state said they believed Mr. Biden would do a better job than Mr. Trump of choosing a Supreme Court justice.
By Saturday morning, Democratic advocacy groups were already targeting Ms. Collins with new, Supreme Court-themed advertising. NextGen America, an organization backed by the billionaire Tom Steyer, released an ad arguing that Americans’ “basic rights are in unprecedented danger” because of the vacancy and voters “can’t trust Susan Collins to do the right thing.”
Fix Our Senate, a Democratic-aligned group, unveiled its own ad campaign opposing a Trump appointment, while a third group, Demand Justice, said it would spend $10 million “to ensure no justice is confirmed before the January inauguration.”
In addition to Maine, Mr. Biden held an advantage on the Supreme Court issue in two other swing states, Arizona and North Carolina, by varying margins, according to the Times poll. In Arizona, voters preferred Mr. Biden by 10 points on the issue, while North Carolinians favored him by a smaller gap of three percentage points.
Mr. Biden has said relatively little about the Supreme Court since securing the Democratic nomination last spring. He pledged during the primaries to make the first appointment of a Black woman to the Supreme Court, though he did not say whether that person would be his first nominee.
Unlike some of his rivals in the primaries, Mr. Biden never embraced proposals from the left to restructure or expand the Supreme Court in order to mute the impact of the two justices Mr. Trump has already appointed. But should Republicans proceed to fill Justice Ginsburg’s seat in a manner widely regarded as underhanded, Mr. Biden could face intense pressure from the progressive wing of the party to embrace those more drastic steps.
A former chairman of the Senate Judiciary Committee, Mr. Biden is himself a veteran of several bruising confirmation struggles, including the successful Democratic effort to thwart the nomination of Robert H. Bork in the 1980s and the process in 1991 that yielded the confirmation of Justice Clarence Thomas.