Democrats have the right idea, but the point needs to be taken further: The U.S. Postal Service needs to be reabsorbed into the federal government proper, and treated as just another public function.
For the majority of its existence, the United States’ Post Office was run as exactly that. It was simply another government department, funded out of general government revenue. If the Post Office charged fees for its services, it did so simply to add to that general government revenue, rather than to “pay its own way.” No one asked if the Post Office was “making a profit” for the same reason no one asks that of the U.S. military: The question doesn’t apply.
Things changed in 1971, when Congress restructured the U.S. Post Office into the U.S. Postal Service, and required it to fund its operations entirely with its own revenue. There was no hard economic reason for hiving the Postal Service off from general government funding. Nevertheless, this division became the conceptual basis for treating the U.S. Postal Service as a market participant, same as a private business, that needs to keep its finances in the black.
Except the Postal Service wasn’t really transformed into the equivalent of a market firm: It’s still required to provide mail service to every corner of the country, for one thing. Its private rivals — FedEx, UPS, Amazon, etc. — are under no such obligation. If you live out in the rural hinterlands, and providing you service isn’t profitable, those companies simply don’t run delivery routes out to you. Only the U.S. Postal Service does. The agency also retains a legal monopoly over certain basic mail services like letter delivery. The idea being that, if the Postal Service’s legal mission requires it to do things private firms wouldn’t do, it should also have some built-in market advantages to make up for that handicap.