Wisconsin is holding its judicial non-partisan elections on April 7, along with Democratic and Republican presidential primaries. On April 4 the Republican National Committee asked the U.S. Supreme Court to disallow a ruling of the lower federal courts, permitting absentee mail ballots to count if they arrive in election administration offices by April 13. The Republican National Committee wants all such ballots to be invalidated unless they have a postmark of April 7 or earlier. Here is the filing. Republican National Committee v Democratic National Committee, 19A1016.
UPDATE: the Democratic response is here.
UPDATE: here is the Republican reply brief.