The court didn't rule on late-arriving mail-in ballots themselves, but will hear another case on the the broader issue this spring.
The justices overrode lower court orders that temporarily froze the cuts, which have been led by the Department of Government Efficiency.
The 51-year-old Jackson is the court’s 116th justice and she took the place of the justice she once worked for.
The Senate has confirmed Ketanji Brown Jackson to the Supreme Court.
Judge Jackson listened to 4+ hours of senators' opening statements on Monday as hearings on her nomination got underway.
The 51-year-old federal judge would be the first Black woman on the Supreme Court, in confirmed.
The Senate Judiciary Committee says confirmation hearings for Ketanji Brown Jackson will begin March 21.
If confirmed, she'd fill the seat on the nine-member court that will be vacated by Justice Stephen Breyer.
Breyer’s departure, expected over the summer, won’t change the 6-3 conservative advantage on the court.
The U.S. Court of Appeals for the D.C. Circuit has issued an administrative stay of a lower court’s ruling ordering former White House counsel Donald McGahn to appear before Congress.