Coronavirus Live Updates: U.S. and Global News

Even as Texas health officials grappled with the surge, the state’s attorney general, Ken Paxton, asked the Supreme Court on Thursday to overturn the Affordable Care Act, which has extended health insurance to more than 1.1 million Texans while protecting state residents who have pre-existing medical conditions.

In legal briefs filed with the court on behalf of Texas and 19 other states, Mr. Paxton argued that when Congress rescinded the tax penalty that the law imposed on Americans who did not purchase insurance — known as the “individual mandate” — the entire law became invalid, a legal argument that has not changed with the pandemic.

“Congress deliberately designed the ACA and its goal of expanding health care coverage around the individual mandate,” Thursday’s brief said. Absent the mandate, it added, other provisions of the law “not only malfunction, but result in the opposite of what Congress intended.”

Although critics have blamed the reopening for contributing to the expanding pandemic, Mr. Abbott has said repeatedly that rolling it back would be a last resort, a stance he repeated on Thursday. Businesses that have already reopened can continue to operate, but any further reopening is halted, he said in a statement. (Bars now operate at 50 percent capacity, while restaurants operate at 75 percent capacity.)

“The last thing we want to do as a state is go backwards and close down businesses,” Mr. Abbott said. “This temporary pause will help our state corral the spread until we can safely enter the next phase of opening our state for business.”

Texas is one of 29 states where case numbers have been rising. The United States reported its largest one-day total since the start of the pandemic on Wednesday: 36,880 new cases, more than two months after the previous high. The resurgence is concentrated largely in the South and West; New York has imposed a quarantine on travelers from many hard-hit states that meet certain health metrics. Florida, Oklahoma, South Carolina and Texas reported their highest single-day totals on Wednesday.