President Donald Trump’s executive order seeking broad changes to how elections are run in the U.S. is vast in scope and holds the potential to reorder the voting landscape across the country, even as it faces almost certain litigation.

President Donald Trump on Tuesday signed an executive order to make sweeping changes to the U.S. election system that critics say threaten to disenfranchise millions of eligible voters.

U.S. citizens are already not allowed to vote in federal elections. But under the order, the national mail voter registration form will require that applicants provide either a U.S. passport, a REAL ID driver's license or state-issued card compliant with REAL standards,