(Bloomberg) -- Senate Judiciary Committee Democrats plan a vote to authorize subpoenas in their inquiry into Supreme Court ethics, and the proposed witnesses would include Harlan Crow, the Texas billionaire whose gifts of undisclosed luxury vacations and other benefits to Justice Clarence Thomas ignited an outcry.

Committee Chair Dick Durbin of Illinois and Democrat Sheldon Whitehouse of Rhode Island announced Monday night that the panel would hold votes on authorizing subpoenas of Crow as well as of Leonard Leo, a conservative legal activist. They said Leo had refused to cooperate with the committee’s investigation, and that Crow has offered partial cooperation, which the Democrats said was inadequate.

The Democrats also want to talk to Robin Arkley II, the chief executive officer of Security National Master Holding Company, LLC. ProPublica reported in June that Arkley had provided free lodging to Justice Samuel Alito at an Alaska fishing lodge he owned.

“Thanks to investigative reporting, we now know that for decades, some justices have been joining billionaires with business before the court on their private planes and yachts or receiving gifts such as private school tuition for a family member,” the Democrats said in a statement. 

Justice Thomas Gift Fight Sets Up Test of Storied Senate Power

“And it is through this reporting that we learned the justices have not been disclosing these gifts as required by federal laws that expressly apply to them.”

Leo equated the Senate investigation in an emailed statement Tuesday to McCarthyism, a reference to Senator Joseph McCarthy’s anti-communist investigations in the 1950s that involved unsubstantiated allegations. 

“I will not bow to the vile and disgusting liberal McCarthyism, that seeks to destroy the Supreme Court simply because it follows the Constitution rather than their political agenda,” Leo said. Leo’s attorneys earlier replied to the committee with objections to the request for information from him.

Crow’s office said in a statement late Monday night that he had made “good faith efforts at a reasonable compromise that respects both sides.”

“It’s clear this is nothing more than a stunt aimed at undermining a sitting Supreme Court Justice for ideological and political purposes,” the statement continued. “Mr. Crow, a private citizen, won’t be bullied by threats from politicians.” The office added, however, that he was committed to “a fair resolution.” 

Thomas said in April that he’d been told that he didn’t have to report the trips.

The high court has come under heightened scrutiny as it renders decisions on politically charged issues like abortion in a country that has become increasingly partisan.

Earlier: Supreme Court’s Thomas Says He Heeded Gift Disclosure Rules

In the Republican-controlled US House earlier Monday, Judiciary Chair Jim Jordan and Oversight Chair James Comer accused District of Columbia Attorney General Brian Schwalb of conducting a politically motivated investigation of Leo. 

The Senate Democrats said Chief Justice John Roberts could address the court’s ethics problems by adopting a binding code of conduct. Roberts has rejected the idea that the court needs its own ethics code. Justice Amy Coney Barrett, however, recently said she supports adopting a formal code.

--With assistance from Billy House.

(Updates with Leonard Leo statement starting in sixth paragraph.)

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