More: That dilemma stems from newly proposed USPS rules that seek to comply with an executive order President Donald Trump signed this spring to crack down on mail-in voting. If courts let the order stand, it would give the federal government an unprecedented role in elections " and could put even more voter data in the hands of Trump officials searching for supposed election fraud.

The proposed rules lay out new conditions that states would have to meet to send ballots through the mail, including giving the agency lists of all voters set to receive mail ballots.

So far, 23 Democratic-led states and the District of Columbia are suing, as are Democratic Party leaders and non-partisan voter advocacy groups, setting up a potentially active summer of high-stakes judicial rulings.