“Physician, heal thyself,” Mr. Grassley told the chief justice.

Mr. Grassley did not list the decisions that troubled him. But he did say that only two members of the court, presumably Justices Clarence Thomas and Samuel A. Alito Jr., “stick to the constitutional text and vote in a consistently conservative way.”

Mr. Grassley’s logic, if that is the right word, was that conservative decisions are apolitical but that liberal ones are partisan.

As for Chief Justice Roberts, Mr. Grassley said, “a number of his votes have reflected political considerations, not legal ones.” Again, the senator did not say which votes he was talking about, but they probably included ones rejecting challenges to the Affordable Care Act.

Chief Justice Roberts has said that the president’s two previous nominees, Justices Sonia Sotomayor and Elena Kagan, were “extremely well qualified for the court.” Yet they were confirmed almost strictly along party lines, he said in remarks in Boston 10 days before Justice Antonin Scalia died on Feb. 13.

“That doesn’t make any sense,” Chief Justice Roberts said. “That suggests to me that the process is being used for something other than ensuring the qualifications of the nominees.”