So much for adult conversation and serious debate about the nation’s debt problem.

President Barack Obama — the very same Obama who’s been calling on political adversaries to act like grown-ups after weeks of budget fights defined by childish taunts and dares — has now reduced the discussion to an even lower level than the one that nearly caused the government to shut down a week ago.

With the Republicans’ tough-minded deficit-reduction plan on the table and the last-minute compromise for the current year setting the stage for meaningful negotiations, the president had an opportunity to demonstrate true leadership, to challenge the country to come to grips with the looming fiscal crisis that threatens to erode America’s standard of living at home and stature as an economic leader around the world.

But did he rise to the occasion? Did he reprise the late John F. Kennedy’s patriotic call to “Ask not what your country can do for you; ask what you can do for your country”?

Nope. At a moment of incalculable historical importance, the president of the United States decided to take the path of least resistance — a cheap and easy road paved with mistrust, envy and resentment. On a day when he could have given his fellow Americans cause for confidence and hope, Obama gave us instead one of the most disappointing moments of a presidency that has all too often left us disappointed.

In his budget speech at George Washington University on Wednesday, Obama promised to reduce the budget deficit by $4 trillion over 12 years but simultaneously and perhaps deliberately may have exacerbated the public’s long-standing deficit of will when it comes to budget-cutting.

By framing the debate as nothing more than rich vs. poor, young vs. old, haves vs. have-nots, Obama set out to turn the most important policy discussion of our time into the trite-and-untrue political argument that Democrats like to pull out of the bottom drawer when they have nothing of substance to contribute: Republicans want to cut taxes for the rich, toss old folks into the street and deny essential services to the poor and disabled.

The patter is so predictable and so irrelevant to the issues at hand that it’s hard to believe anyone still takes it seriously.

But Obama’s boosters in the mainstream media led the cheers as if the speech had been written just for them.

“President Obama, Reinvigorated” blared the headline over The New York Times’ editorial.

The Times praised the president’s message, saying he “used his budget speech to clearly distance himself from Republican plans to heap tax benefits on the rich while casting adrift the nation’s poor, elderly and unemployed. Instead of adapting the themes of the right to his own uses, he set out a very different vision of an America that keeps its promises to the weak and asks for sacrifice from the strong.”

Be still, our bleeding hearts.

The “strong” are sacrificing plenty in this country. A small percentage of Americans carry an undue share of the tax burden — and those at the top of the economic scale drive much of the economy through investment and job creation.

But even if we concede that the wealthiest Americans should pay more taxes, that does little or nothing to erase our budget deficits and burgeoning national debt. It would be one thing if increased revenue from higher taxes were committed to debt reduction. But we’ve seen it time and time again: Give Congress and/or the federal bureaucracy a dollar, and they will spend it.

America’s debt problem can be addressed only by reining in the government’s out-of-control penchant for spending money, and by reforming or restructuring entitlement programs such as Medicare and Medicaid.

The overhaul of these programs proposed by the House Budget Committee chairman, Republican Rep. Paul Ryan of Wisconsin, may be more drastic than the country is willing to accept. But the president’s plan for Medicare amounts to the same pie-in-the-sky projections for reducing costs that Democrats used in creating the fiction that the health care reform program they enacted last year would reduce the deficit, not add to it.

As we have said previously, Ryan’s plan is unlikely to survive in its original form, but it’s a legitimate and serious starting point for dealing with deficits and debt.

President Obama could have and should have countered with something equally as legitimate — something that could lead to real debate and real progress toward guaranteeing the nation’s economic stability. Instead, he gave us divisive rhetoric and lame sloganeering.

Truly disappointing.