But the ultimate fate of the subpoenas is uncertain. If Crow and Leo defy the information requests — which ask for a detailed accounting of gifts, transportation and lodging the two men provided or helped organize for Supreme Court justices and the justices’ relatives — Democrats would need a 60-vote majority to enforce the subpoenas. Currently, Democrats hold a one-vote advantage in Congress’ upper chamber.

Republicans have mounted fierce opposition to the inquiry into Crow and Leo, who have for months refused to comply with the committee’s requests. The vote to issue the subpoenas fell along party lines, with all 11 of the Democrats voting in favor and most Republicans walking out of the hearing in protest as the vote was taken.

Sen. Dick Durbin, D-Ill., the Judiciary Committee chairman, said at Thursday’s hearing that the revelations reported by news organizations including ProPublica spurred the committee’s action to demand more information about people close to the justices.