That order has raised alarms inside the Postal Service over whether it can or should take on such a complicated and controversial role, sources told CNN, especially when it may need help from Trump and Republicans to steady its finances.

Under the order, the Postal Service would work with states to determine who can vote by mail and enforce that eligibility, flagging or rejecting ballots tied to people not on those lists. Voting-rights groups and some Democratic-led states say that’s an unconstitutional power grab: The Constitution gives states — not the president or USPS — control over election administration.

“USPS is no longer merely a carrier of ballots; it is instead transformed into a gatekeeper of voter eligibility,” lawyers challenging the order wrote.

Even as the lawsuits move through federal court, the order directs the Postal Service to begin the first stage of implementation — its rulemaking process — by the end of May. The Postal Service says it’s begun that process, but current and former postal officials question whether a cash-strapped USPS could take on a sweeping new election role — or whether its independent board could refuse.