Patrick Marley

This new system was supposed to be up and running as of yesterday, but Trump's order has been temporarily blocked by a federal judge.

Patrick Marley, who covers voting issues for The Washington Post, told us how the system works.

They want the states to upload lists of voters who are eligible to receive mail ballots through a new, as-yet-unseen online portal to the Postal Service.

It would include a complex voter verification process where postal workers cross-check that the people on their list to receive mail ballots are also on the state's voter rolls.