Commuters at the McPherson Square Metro station on March 30. (Ricky Carioti/The Washington Post)

WASHINGTON’S SUBWAY system, already beset by daily service snafus and frighteningly frequent major mishaps, risks a downward spiral in its finances. Even as despairing customers quit Metro and local politicians heap scorn on it, the system needs billions of dollars in the short and medium term, without which it is virtually certain that things will grow worse.

The paradox is how to generate support for new infusions of money — to rescue, maintain and improve a degraded network — even as the system’s passengers and political patrons abandon it amid accelerating decay.

Metro’s problems are not only the product of underinvestment; poor management and a cavalier approach to maintenance and safety share equal billing. But it is also true that better management will not suffice in the absence of more money.

The price tag will run to multiple billions and must be shouldered by all three of Metro’s localities as well as the federal government. To date, local and federal leaders have found it easier to wring their hands than get them dirty crafting forward-looking solutions.

Alone among major transit systems, Metro lacks a dedicated source of funding, leaving it dependent on the whims of appropriators. The agency needs a champion who will advocate for a steady new income source. The last such champion was then-Rep. Thomas M. Davis III (R-Va.), who, shortly before leaving Congress in 2008, engineered a deal to sustain Metro’s long-term projects — $300 million split between the feds and localities.

That deal ends in two years, and the cash it generates, which now looks quaint compared with Metro’s liabilities, will be gone by 2020. So it’s time for regional leaders and federal officials to take a frank look at what saving Metro will cost. And let’s hope it’s a more constructive look than was mustered by Rep. John L. Mica (R-Fla.), whose only response, upon hearing of Metro’s needs, was to call the system a “screwed-up mess” and say, “I’m not going to bail you out.”

Real leadership would engage with hard realities. Metro reckons its current six-year, $6 billion capital budget for major projects needs to double within a few years simply to restore the subway to a state of good repair. An additional $500 million annually in major construction is the minimum necessary to ensure the system does not backslide again a decade from now. Over the coming 10 years, the system also faces an operating deficit, simply to keep the trains running, amounting to several hundred millions dollars annually, resulting from projected expenses growing more than twice as fast as projected revenue. And Metro’s pension and health-care commitments to its retirees are more than $2 billion in the red.

Politicians such as Mr. Mica, who signed Grover Norquist’s pledge never to raise taxes, are grandstanders; Mr. Mica’s only suggestion was that Metro’s general manager, Paul J. Wiedefeld, should “fire people.” In place of such hot air, a real champion for Metro on Capitol Hill could make a difference. Will anyone step into the breach?