WASHINGTON — As President Trump prepares to name a new justice, one reality is increasingly clear about the Supreme Court — it has become another polarized institution in the polarized capital of a polarized nation.
The string of politically charged 5-to-4 decisions that punctuated the end of the court’s term highlighted how thoroughly the tribal politics that have engulfed the White House and Capitol Hill have now ensnared the court. In deciding major cases with clear political overtones, an extremely reliable indicator of what side a justice would come down on was whether he or she was appointed by a president with an “R” or a “D” behind his name.
“It is clearly the most partisan court ever, where you can actually look at Republican and Democrat and use that as a proxy for voting and behavior on the court,” said Neal E. Devins, the Sandra Day O’Connor professor of law at the College of William and Mary, who has studied the partisan evolution of the court.
And this is before Mr. Trump’s virtually certain nomination of another conservative, a development expected to make the partisan divide even more stark. With one recent poll showing that half of American voters believe the Supreme Court is driven mainly by politics, lawmakers in both parties worry that the perception is destroying trust in the court as a supposed neutral arbiter of the United States’ political and policy disputes.
“People expect that the executive and legislative branches are going to be political, but the judiciary is supposed to be above the fray,” said Senator Susan Collins, Republican of Maine, whose vote is likely to be pivotal in the coming confirmation fight. “But when you talk about ideological blocs on the court, then you are eroding the public’s faith in the judicial system and the rule of law, and I think that is really serious.”
Senator Patrick J. Leahy, Democrat of Vermont and a longtime senior member of the Judiciary Committee, said the rising partisanship of the judiciary presents a major obstacle for the Supreme Court if it comes to be viewed mainly as a creature of politics.
“They have a huge image problem,” Mr. Leahy said. “I am…