The Postmaster General is warning that a postal budget crisis could cause mail delivery to be consolidated to just three days a week. Meanwhile, the American Postal Workers Union (APWU) is trying to convince lawmakers—and taxpayers—to keep all its union jobs.

The APWU’s new radio ad airing in Washington, D.C., says the pounds of mail handled by workers don’t cost you “a single cent.”

“The United States Postal Service doesn’t run on your tax dollars. It’s funded solely by stamps and postage,” the 30-second ad says. That’s technically true (unless you count the legally enforced monopoly on first-class mail as a subsidy). Unless some real reforms are made in how the USPS operates, however, that will change. The USPS owes $5.5 billion—due September 30—to future retirees’ health benefits, which the Postmaster General says it can’t pay. Its continuous hemorrhaging of money is creating the looming specter of a postal bailout.

According to the APWU, the ad is a direct response to Representative Darrell Issa’s (R–CA) proposal to allow USPS to eliminate Saturday mail delivery. Issa’s plan goes much further than that—he proposed ending the ban on closing unprofitable post offices and aligning compensation more closely with the private sector. He also proposed changing collective bargaining and requiring workers to pay more toward their health and life insurance—reforms that no doubt got the union’s attention.

The Postal Service employs three times as many union members as the U.S. auto industry, and, like the auto industry, employee benefit costs are crushing it. Just last month, the Postal Service had to suspend contributions to employee pensions because the agency is already drowning in red ink. Postal employees also earn 15 percent to 20 percent more per hour than comparable workers in the private sector.

The APWU ad will run for three weeks on “news and/or talk stations in Washington DC and other markets,” the union says. The campaign includes TV advertising on cable news channels and print ads in Capitol Hill–centered publications.

APWU president Cliff Guffey said, “The campaign is designed to inform the American people about the work our members perform and to dispel the persistent myth that the Postal Service is funded by taxpayers.”

If drastic changes are not made, this myth could quickly become reality.