Voting in Wisconsin will proceed as scheduled on Tuesday, after conservative majorities on the federal and state supreme courts blocked Democratic efforts to extend balloting for days or weeks to reduce public gatherings during the coronavirus pandemic.

Late Monday, the U.S. Supreme Court by a 5-4 vote overturned lower-court orders extending by six days the deadline for mailing absentee ballots. The high court’s action came shortly after the Wisconsin Supreme Court invalidated an executive order by Gov. Tony Evers rescheduling...