The order calls for limiting mail ballots and using federal data to compile lists of eligible voters – moves experts say exceed his constitutional authority.

States are already preparing for the possibility that the Supreme Court could eliminate grace periods for mail-in ballots received after Election Day, which could pose unexpected consequences for this year’s midterm elections and beyond.

In biennial state elections in Massachusetts, which are the November elections every two years where state and federal positions like district attorney, governor, U.S. representative, U.S. senator and president can be voted on, ballots are accepted up to three days after the election, as long as they are postmarked by election day.

U.S. President Donald Trump has repeatedly attacked the legitimacy of mail-in ballots via false and misleading claims.

A decision to limit late-arriving mail-in ballots could overturn laws currently allowing it in 14 states and Washington, D.C.