The Gallery Place and Chinatown Metro Station in Washington. (Marvin Joseph/The Washington Post)

JUST AS the region has started coming to grips with reversing Metro’s years-long death spiral, top officials in the District are throwing a wrench in the works that could kill any chance of righting a transit system whose maintenance and safety problems have imperiled its future and the region’s.

The proposal from the District, put forward most vocally by D.C. Council Chairman Phil Mendelson (D), involves how the District and Metro’s suburban stakeholders, Maryland and Virginia, would share the $500 million in additional annual capital spending that is a bare minimum for restoring the system to good health after decades of underfunding.

Mr. Mendelson proposes a radical overhaul of the funding formula in place since Metro’s founding in the 1970s. Its effect — a massive transfer of the cost-sharing burden from the District to the suburbs, especially Northern Virginia — is a recipe for impasse, inaction and inertia, the very ingredients that, over the course of decades, led to Metro’s impoverishment and meltdown.

Mr. Mendelson advocates a cost-sharing system that would impose a flat, across-the-board regional sales tax to be paid equally by every individual in the District; in Maryland’s Montgomery and Prince George’s counties; and in the half-dozen Northern Virginia localities served by Metro. Mr. Mendelson insists his proposal is equitable. Since Metro is a regional system, he says, why shouldn’t everyone in the region pay equally?

In fact, what he proposes is unfair. Under his blueprint, Northern Virginia, which under the existing system would shoulder roughly 31 percent of Metro’s capital expense in 2020, based mainly on ridership and number of subway stations, would pay more than half the annual $500 million tab. By contrast, the District, which now pays about 36 percent of capital costs, would have its bill slashed by more than a third, to about $115 million. (Maryland’s bill would also be cut, by about 20 percent.)

That approach fails on grounds of equity and logic. The District is much more heavily dependent on Metro than sprawling and far more populous Northern Virginia, whose “downtown,” Tysons Corner, boomed for a half-century before Metrorail opened there just three years ago. As a percentage of population, the District’s subway ridership is far higher than Northern Virginia’s. And the District has 40 Metrorail stations vs. Northern Virginia’s current 25.

Why upend the existing cost-sharing formula? A subject of compromise years ago, it is flexible, adjusting jurisictional burdens as ridership shifts and new stations open. Where the system fails is that it yields no earmarked, reliable, ongoing funding source.

To launch a debate on a new formula is to open a can of worms. It is a political non-starter in Virginia’s Republican-dominated legislature, which would never approve it. It makes Metro a political football just as the system, under its best management team in years, has started to get its house in order. It nearly ensures gridlock, the likely result being the departure of Metro’s highly regarded general manager, Paul J. Wiedefeld.

A game of brinksmanship with the District’s suburban partners amounts to a death wish for Metro — not exactly the right strategy for a system already on the brink.