The decision to try to compel cooperation from a leading judicial activist and a Republican megadonor came over fierce G.O.P. opposition and threats of retaliation.
The Judiciary Committee postponed votes to issue subpoenas for benefactors of Justices Clarence Thomas and Samuel Alito after Republicans threatened a politically charged fight.
With hard-right Republicans attacking federal law enforcement agencies and unwilling to extend their broad powers, a major warrantless surveillance program targeting foreigners overseas may face new limits from Congress.
In a new letter, Democrats on the Judiciary Committee asked Harlan Crow, a billionaire with extensive ties to Justice Clarence Thomas, to provide a list of any benefits he provided.