President Trump’s campaign filed a motion Wednesday to join in the Pennsylvania Republican party’s appeal to the U.S. Supreme Court in an ongoing dispute about mail-in ballots received after Election Day. If successful, that appeal could invalidate any votes received by processing centers after Election Day. Last week, the Supreme Court refused to expedite that appeal and hear it before the election, but requested that Pennsylvania separate the “late” ballots so that they could be challenged later.

The Supreme Court motion is one of many legal maneuvers the campaign vowed to pursue on Wednesday as counting continued. Pennsylvania laws prevent poll workers from processing them until closing time on Election Day, leaving poll workers with millions of uncounted mail-in votes on Wednesday morning. In the state capitol and Democratic stronghold of Philadelphia alone, hundreds of thousands of votes have been unaccounted for, CNN reported.