Three leading election integrity groups urged the Supreme Court on Thursday to prohibit states from counting mail-in ballots that arrive after Election Day, warning that the practice violates federal law and undermines public trust in elections.

In a new amicus curiae brief filed Thursday afternoon, the Honest Elections Project, Restoring Integrity and Trust in Elections, and the Center for Election Confidence backed the Republican National Committee and Mississippi Republican Party, urging the justices to enforce a uniform deadline requiring all ballots in federal elections to be received by the close of polls on Election Day.