The ruling was 5-4, with the court's conservatives in the majority.
The decision followed a familiar pattern on the court. But it was striking that in a case with partisan implications in the midst of a national crisis, the court could not find a way to overcome its usual differences.
In its brief order, the court majority said a plan ordered by a district judge and approved by an appeals court to extend absentee voting for a week was "extraordinary relief and would fundamentally alter the nature of the election."
A "critical" point, it said, was that the relief was more than had been asked for by Democrats and liberal groups.
The unsigned opinion by Chief Justice John Roberts and Justices Clarence Thomas, Samuel Alito, Neil Gorsuch said Brett Kavanaugh granted a request from the Republican Party to put the plan on hold.
The lower court's decision "contravened this court's precedents" and violated the Supreme Court's repeated instruction that "lower federal courts should ordinarily not alter the election rules on the eve of an election."
All of the court's conservatives were nominated by Republican presidents.
The court's liberals -- Ruth Bader Ginsburg, Stephen Breyer, Sonia Sotomayor and Elena Kagan, all nominated by Democratic presidents -- objected sharply.
"This court now intervenes at the 11th hour to prevent voters who have timely requested absentee ballots from casting their votes," Ginsburg wrote.
She said it "boggles the mind" that the court majority was trying to apply the court's usual rules in an unprecedented time of national turmoil.
"While I do not doubt the good faith of my colleagues, the court's order, I fear, will result in massive disenfranchisement," Ginsburg wrote. She noted delays in a crush of applications for absentee ballots.
"A voter cannot deliver for postmarking a ballot she has not received."
Ginsburg said the majority had misplaced its priorities.
"The concerns advanced by the court and the applicants pale in comparison to the risk that tens of thousands of voters will be disenfranchised," she wrote. "Ensuring an opportunity for the people of Wisconsin to exercise their votes should be our paramount concern."
Lower courts had said voters should have another week -- until April 13 -- to return absentee ballots, because the state was unable to accommodate in-person voting.
The Supreme Court had not been asked to review the other legal wrangling in the state, as the governor moved to postpone the election, and the Wisconsin Supreme Court ruled he lacked authority.
Instead, the justices were considering legal victories Democrats and liberal groups won last week in federal court.
U.S. District Judge William Conley declined to postpone in-person voting, but extended absentee voting until April 13, and a panel of the U.S. Court of Appeals for the 7th Circuit on Friday upheld much of Conley's ruling.
On Saturday, Wisconsin Republicans and the Republican National Committee brought the issue to the Supreme Court.
Lawyers for the Republicans said the appeals court's decision "creates a fundamental unfairness that undermines the integrity of the election" and would encourage gamesmanship.
"Absentee voting should not be a procedure that gives some voters dramatically different incentives and information than others, permits advocacy groups to strategically chase down ballots that were not cast on election day, and otherwise disrupts Wisconsin statutes that aim to separate cleanly the time for ballot casting and ballot counting," lawyers said in their brief.
But lawyers for Democrats said that not recognizing the effect of the coronavirus pandemic on the election would be irresponsible.
The plans devised by the lower courts are "reasonable remedies for the extreme, unprecedented circumstances that tens of thousands of Wisconsin voters are likely to face: either they venture out to vote in person and risk their health and the health of others, or they forfeit the right to vote through no fault of their own," their brief said.
They said judges have the power to demand that local officials not announce any results from the election until April 13, which would contain Republican concerns about gamesmanship.