Here’s the critical thing to understand about President Obama’s budget speech: There’s a difference between what political consultants call the “message box” and what I’ll call the “solutions box.” Obama’s message box will work. His solutions box won’t. And there, in a nutshell, is why America remains at risk of drift and decline.

In campaigns, political advisers often develop message boxes for candidates to frame the debate on their terms. They do everything they can to ensure that the media and public see the debate the way the campaign wants it to be seen.

There is, however, no necessary link between what it takes to win an election and what it takes to address the country’s major challenges. And, unfortunately, between now and November 2012 we’ll be treated to dueling attempts to define the debate, in ways that bear little relationship to real answers.

Obama succeeded Wednesday in shaping a message box that puts him in a good position to win reelection if (1) he faces only a Republican opponent and (2) that Republican embraces anything like Rep. Paul Ryan’s budget blueprint. That doesn’t mean Obama’s framework can solve America’s problems and make good on the rhetorical vision the president sketched.

When Obama says he wants to cut the deficit $4 trillion over 12 years, it’s an attempt to get the media and the public to conclude something like: “Well, both the president and the GOP want to cut the deficit a huge amount, but it’s the way they want to do it that’s different.” That’s the president’s overarching message — we all want fiscal responsibility, but there’s a “balanced” way to do it and an “extreme” way.

Once inside that framing, when Obama says that we won’t abandon our commitments to seniors or the poor in order to cut taxes by a trillion dollars for millionaires — “not while I’m president!” — he’s signaling his values. Values that a large majority of Americans share (me included). Except there’s more to a plan than its values. Like, for instance, efficacy.

Here’s the kind of question sure to be lost in the partisan fight: Why is $4 trillion in deficit reduction over 12 years the right goal? The political answer is easy: It sounds big, it’s equal to the Simpson-Bowles commission’s target (Obama’s goal is met over 12 years, not 10 as the commission proposes, but who’s counting?) and it’s close enough to Ryan’s number to establish the idea that “we both want to get serious.”

But as a matter of substance, the goal is utterly inadequate. Ryan’s “bold” plan, after all, still adds a whopping $6 trillion to the debt in the next decade. As for Obama’s plan, if deficits are still going to be well over 2 percent of gross domestic product in the last half of this decade (as a White House fact sheet says), I’m guessing Obama’s framework will rack up perhaps $8 trillion or more in fresh debt over the next 12 years.

Why do neither Obama nor the Republicans propose to actually balance the budget much sooner? Because the president and the GOP don’t want to tell Americans that taxes on the middle class will have to rise and benefits be trimmed (starting soon, not a decade out, as the Ryan plan does), as the boomers age. With candor ruled out, they’re left acting as if solvency is the proper goal regarding our debt — how much relative to gross domestic product can we stand before markets go bonkers? — when the real goal should be a budget plan that promotes national renewal.

The endless debt that comes with these slow-as-molasses fiscal adjustments means interest payments will continue to drown out other priorities within any given level of spending. Under Ryan’s plan, for example, interest soars from around $200 billion to nearly $700 billion a decade hence. Obama’s interest black hole will surely be higher.

Having interest on the debt be America’s fastest-growing program in an era of supposedly “epic” deficit-reduction plans isn’t just Orwellian; it’s a recipe for national decline. Between the debt vacuum, and the senior-benefits vacuum as the baby boomers age, the portion of federal spending devoted to infrastructure, research and education will shrivel. No matter how many times you vow to “win the future,” if your budget funds only the past and the present, you don’t stand a chance.

Is Obama’s framework better than Ryan’s? Absolutely. Is it equal to what America needs for renewal in an age of global competition? Absolutely not. It’s Clinton redux — a recipe for incremental progressive “wins” within a broader context of national erosion.

We need a third choice. We’ll never know if a constituency exists in America for a message box that lines up with the solutions box until one is actually offered. We’re poised to go through another presidential cycle in which average Americans are told they don’t need to participate in getting our fiscal house in order. Yet anyone who looks honestly at the numbers knows this is false.

The party lines have been drawn. The only question is whether anyone serious will jump in outside the two-party system to shake things up.

Matt Miller, a senior fellow at the Center for American Progress and co-host of public radio’s “Left, Right & Center,” writes a weekly online column for The Post.