Can U.S. politics still deliver in the public interest? A test case is taking shape in the Washington area.

The test is this: Can the transit system of the nation’s capital be saved?

On one level, a rescue should be easy. Pretty much everyone, even people who don’t use Metro, agrees that its demise would be a disaster. Pretty much everyone agrees that Metro desperately needs help. And while there isn’t quite the same consensus on a solution, what needs to be done also is pretty well understood.

Yet if you had to place bets right now, you’d be cautious wagering on a happy ending. And the reasons for that say a lot about the challenges U.S. politics confront across the country.

Some of Metro’s difficulties are particular to the system. Multiple jurisdictions, including two states, the federal government and the District of Columbia, help manage and support it, so no one official is accountable for its success or failure.

But its problems more generally stem from a failure to face hard choices honestly that echoes loudly through state and federal governance.

For years, Metro’s overseers have been more inclined toward crowd-pleasing system expansion than needed but unsexy maintenance.

For years, they were happy to buy labor peace by promising generous retirement benefits that would come due down the road, on somebody else’s watch.

For years, politicians have been unwilling to acknowledge that no modern transit system can support itself on fares alone but will need steady, dedicated tax revenue as well.

The result, Metro General Manager and Chief Executive Officer Paul J. Wiedefeld said during a visit to The Post last week, is a system that was once the “gold standard” for mass transit but is now not even bronze. Wiedefeld, who took over in 2015, said it has been “amazing to me that it could slip so far.”

Metro’s operating costs are rising nearly twice as fast as its revenue, Wiedefeld said, and that is apart from $25 billion in capital needs — for new cars and the like — over the next 10 years. If something doesn’t change, fares will keep rising while ridership and service decline.

In his first 17 months on the job, Wiedefeld concentrated on safety improvements and intensive track repair. Now he has put forward a plan that would restore rail and bus service to sustainability.

The plan asks all the jurisdictions to dedicate a source of revenue to Metro, as every other region with a transit system (including New York City, Los Angeles and Chicago) does. In return it would cap the growth of operating subsidies at 3 percent per year.

It protects retirement benefits for existing employees and retirees, but would give a less cushy deal to those hired in the future. Work that is union now would stay union, but Metro would have the option to contract out some new components of the system, though unions would be allowed to compete for the work.

There’s something here to make everyone unhappy, in other words, and initial reviews rolled out accordingly. A union statement called the plan “bad for riders, bad for workers and bad for the region,” while Maryland’s Republican governor grumbled about a statewide tax that nobody had proposed. (The burden would more likely fall on Prince George’s and Montgomery counties.)

That kind of first reaction is predictable. But here are some things to watch for next.

Will local politicians have the courage to stand up to core constituencies for the common good? Will Democrats such as Maryland Reps. Jamie B. Raskin and Anthony G. Brown tell the unions that they are better off saving most of their jobs and benefits than driving the system into bankruptcy while waving the flag of purity? Will a Republican such as Virginia Rep. Barbara Comstock tell members of her party that Metro needs a dedicated tax, or will she be forever moving the reform goalposts?

The federal government would be in big trouble without Metro. Will Transportation Secretary Elaine Chao step up?

And if gubernatorial candidates in Virginia, state delegates and city council members in all three jurisdictions and U.S. senators from both states opt for compromise and honesty, will voters punish or reward them? The answer to that question could spell the difference between a prosperous, growing capital region and one that chokes on its own traffic as a $40 billion onetime jewel wastes away.

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