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.
He was equally involved in efforts to strike down affirmative action by colleges and universities. He played a supporting role in Fisher v. the University of Texas, a case that originated in 2008 and came before the Supreme Court twice. In both instances, the university successfully defended its plan to automatically admit in-state students who had graduated in the top 10 percent of their class.
Mr. Consovoy then worked closely with Mr. Blum on cases against Harvard and the University of North Carolina, arguing that their affirmative action programs — and, by extension, college and university affirmative action programs generally — were unconstitutional.
Those cases, brought on behalf of Students for Fair Admissions, an organization that Mr. Blum founded, reached the Supreme Court last fall. By then, Mr. Consovoy was too ill to argue them himself, so two of his partners did instead. The court is widely expected to decide in favor of Students for Fair Admissions before the end of the term, most likely in June.
“He was an enormously talented legal strategist,” Mr. Blum said in a phone interview. “He was the quintessential legal chess player. He knew, if he made a move in this direction, what the first four options his adversaries would take. He knew every argument, the upside of the argument, where we’re vulnerable, where we’re strong.”
In 2014, Mr. Consovoy and Mr. McCarthy, who had also clerked for Justice Thomas and who was also at Wiley Rein, left that firm to found Consovoy McCarthy.
The new firm took on a variety of cases, not all of them concerned with constitutional matters but most of them in service of conservative causes and ideas. After Uber announced in 2020 that its food-delivery branch, Uber Eats, would waive fees for Black-owned businesses, Consovoy McCarthy arranged for some 31,000 complainants to claim reverse discrimination through arbitration, leaving the company owing as much as $92 million.
Mr. Consovoy represented Mr. Trump in his fight to prevent Congress from forcing the release of his tax returns. In doing so, he advanced the controversial legal argument that Congress had virtually no capacity to investigate the president beyond an explicit legislative agenda — even if the president were involved in illegal activity.
Despite his clear conservative leanings, Mr. Consovoy won praise from many of his legal sparring partners on the left, both for his acumen and for the dispassionate way he approached his ideologically contentious cases.
“I think he was one of the greatest lawyers of our generation,” Neal Katyal, an acting solicitor general for President Barack Obama, said in a phone interview. “In hot-button cases, lot of times passions overtake logic, and that was not the case with him. So in court it wasn’t cheap appeals to emotion or anything like that. It was just good legal argument.”
William Spencer Consovoy was born on Aug. 31, 1974, in Plainfield, N.J. He grew up in nearby Florham Park, where, like any self-respecting Garden State native, he developed a lifelong love for the Philadelphia Eagles and Bruce Springsteen.
He came from a family steeped in New Jersey politics. His paternal grandfather, George, served as mayor of Franklin Township, in the middle of the state, in the 1960s.
His father, Andrew, was the chairman of the state parole board, though he was forced to resign after being accused of trading favors with people involved in organized crime. He denied the accusation, and no charges were ever brought.
William’s mother, Linda Whalen, was a mental-health specialist. Both she and his father survive him, as do his stepfather, Bernie Whalen, and his sister, Amanda Consovoy. He married Masa Anisic in 2020. She died in 2021, also from cancer.
Mr. Consovoy graduated from Monmouth University in 1996 with a degree in political science, and from the Antonin Scalia Law School at George Mason University in 2001. There, he became a devotee of Justice Thomas, captivated by his no-holds-barred originalism.
“For Justice Thomas, I believed, judging was not about slogans, labels or legal theories,” Mr. Consovoy said in a 2016 speech at George Mason. “It was about the search for truth.”
He clerked for Judge Edith Jones of the U.S. Court of Appeals for the Fifth Circuit before becoming the first student from George Mason’s law school to clerk for the Supreme Court. His success helped distinguish the school, in the Virginia suburbs outside Washington, as a hothouse of conservative legal thinking and training.
Though he quickly made partner at Wiley Rein, he grew restless within the confines of a large firm. He and Mr. McCarthy steadily expanded their firm from a two-man start-up to a 22-lawyer operation.
For all his ferocious defense of conservative causes, Mr. Consovoy was known for his ability to contain an argument to the courtroom, never letting an opponent become an enemy.
“Most people either shy away from those kinds of cases, or do them and then get consumed by them,” Mr. Katyal said. “That was not the case with him. And that’s actually, sadly, a rare thing.”