William Consovoy, a rising star within the conservative legal firmament who made his name arguing landmark cases on election law and affirmative action, often before the Supreme Court, and who represented President Donald J. Trump in his effort to keep his tax returns private, died on Monday at his home in Falls Church, Va. He was 48.
Thomas McCarthy, a close friend with whom he founded the firm Consovoy McCarthy, confirmed the death. Mr. Consovoy was diagnosed with brain cancer in 2020 and stepped away from litigation last fall.
Over the course of a relatively short career, Mr. Consovoy established a reputation as one of the best and most dogged conservative litigators before the Supreme Court, with a penchant for cases aimed at making major changes to America’s constitutional landscape.
He clerked for Justice Clarence Thomas during the 2008-9 Supreme Court term, and he came away with the conviction that the court was poised to tilt further to the right — and that constitutional rulings that had once been considered out of reach by conservatives, on issues like voting rights, abortion and affirmative action, would suddenly be within grasp.
Mr. Consovoy was perhaps best known for his work with Edward Blum, the conservative activist who engineered the effort to have the Supreme Court overturn Section 4 of the Voting Rights Act and, more recently, to outlaw affirmative action in higher education.
In 2013, in one of his early cases before the Supreme Court, Mr. Consovoy successfully argued the Section 4 case, Shelby County v. Holder, persuading the Court to get rid of the requirement that several states and counties, mostly in the South, had to receive federal clearance before changing their election laws.
“From the beginning of Shelby, Will was helpful in conceiving the case and maneuvering it to the court,” Bert W. Rein, a founder of Wiley Rein, where Mr. Consovoy worked until 2014, said in a phone interview. “Will was just critical to all of that.”
The decision set off a wave of new voting laws, including limits on early and absentee voting.
Mr. Consovoy often led the charge in attacking existing laws in court or defending new ones. In 2020 alone, he argued against an extension of the deadline for mail-in ballots in Wisconsin, the re-enfranchisement of felons in Florida and a California plan to send absentee ballots to all registered voters.
Condolences to his family and friends.