The idea that Mr. Trump would pick from a list developed by conservatives has inflamed some Democrats, including Senator Bob Casey of Pennsylvania, who declared that he would vote against Mr. Trump’s nominee even before the choice was announced Monday night.
“Any judge on this list is fruit of a corrupt process straight from the D.C. swamp,” Mr. Casey said in a statement.
The political left, naturally, has its own advocacy organizations and lists of favored candidates when Democratic presidents have Supreme Court vacancies to fill. For the most part, in fact, the four-member bloc of Democratic appointees on the court — Ruth Bader Ginsburg, Stephen G. Breyer, Sonia Sotomayor and Elena Kagan — has voted more in lock step than the Republican appointees.
But liberals lost their chance to solidify a left-leaning majority on the court when Senate Republicans refused to consider President Barack Obama’s nomination of Judge Merrick B. Garland in 2016 after the death of Justice Antonin Scalia, the court’s conservative stalwart. That seat ultimately went to Justice Gorsuch, keeping it in the court’s right-leaning faction.
If Judge Kavanaugh follows Mr. Gorsuch’s example so far, Chief Justice Roberts may become the major swing vote. He has surprised, and disappointed, conservatives on occasion, most notably when he voted to uphold the constitutionality of Mr. Obama’s health care program. But Chief Justice Roberts has still been much more reliably conservative than Justice Kennedy.
Still, some longtime legal scholars said it would be a mistake to assume that Judge Kavanaugh’s appointment would change the court fundamentally for the foreseeable future. “The possibility of drift is always there,” Mr. Levey said. And if a Democrat were to win the White House in 2020, a conservative vacancy could still swing the court back.
“People say this will cement a conservative court for a generation,” said Michael W. McConnell, a former appeals court judge who was considered for the Supreme Court by Mr. Bush. “I don’t think that’s true. The court goes back and forth and, personally, I think it’s rather a good thing that the court have solid representations from both perspectives. This is a divided country.”