NEW YORK — Two election watchdog organizations sued President Donald Trump’s administration on Monday over his executive order seeking to overhaul the nation’s elections through a proof-of-citizenship requirement, new mail ballot deadline restrictions and other sweeping changes.

The lawsuit, filed by the Campaign Legal Center and the State Democracy Defenders Fund in the U.S. District Court for the District of Columbia, asks the court to declare the order unconstitutional and stop it from being implemented.

It names three nonprofit voter advocacy organizations as plaintiffs that it alleges are harmed by the order: the League of United Latin American Citizens, the Secure Families Initiative and the Arizona Students’ Association.

“The president’s executive order is an unlawful action that threatens to uproot our tried-and-tested election systems and silence potentially millions of Americans,” said Danielle Lang, senior director of voting rights at the D.C.-based Campaign Legal Center. “It is simply not within the president’s authority to set election rules by executive decree, especially when they would restrict access to voting in this way.”

The White House didn’t immediately respond to a request for comment.

Monday’s lawsuit marks the first major legal challenge to last week’s executive order, which election lawyers have warned may violate the U.S. Constitution and asserts power they say the president does not have over an independent agency. That agency, the U.S. Election Assistance Commission, sets voluntary voting system guidelines and maintains the federal voter registration form.

It comes as Congress is considering codifying a proof-of-citizenship requirement for voter registration into law, and as Trump has promised more actions related to elections in the coming weeks.

The lawsuit draws attention to the Constitution’s ” Elections Clause,” which says states — not the president — get to decide the “times, places and manner” of how elections are run. That section of the Constitution also gives Congress the power to “make or alter” election regulations, at least for federal office, but it doesn’t mention any presidential authority over election administration.