Political science data tends to support the politicians rather than the justices when it comes to whether politics plays a part in judges’ decisions. The data demonstrates a significant correlation between judges’ political affiliations and their voting.

Some Democrats have floated proposals to take into account that reality. Pete Buttigieg, the mayor of South Bend, Ind., and a 2020 presidential candidate, for instance, has outlined a plan based on a paper from two law professors, Daniel Epps of Washington University in St. Louis and Ganesh Sitaraman of Vanderbilt, to mandate ideological balance on the Supreme Court. Under that proposal, the number of justices would grow to 15 from nine: five affiliated with the Republican Party, five affiliated with the Democratic Party and five others selected by the first 10 based on their “fairness, independence and centrism.”

Such proposals face practical hurdles and constitutional objections. But, particularly in light of the stormy confirmation hearings last year for Justice Brett M. Kavanaugh and their lingering aftershocks, there are reasons to think that ideological balance would be good for the court.

Several justices have said that they worked much harder to come together in the year that they were short-handed after Justice Scalia’s death. That eight-member court included four Republican appointees and four Democratic ones. It reached a modern record for consensus.

The debate over the role politics plays in judging is mostly theoretical. But a petition filed this month by Gov. John C. Carney Jr. of Delaware, a Democrat, makes it concrete. It asks the justices to consider whether states may take account of the political affiliations of judges to try to achieve something like ideological balance on their courts.