“An adult conversation” — that’s what we need to have about spending, President Obama proclaimed at a Feb. 15 presser. The president’s hardly the first to use that cloying, self-congratulatory phrase: so many House Republicans mouthed it in November that Jon Stewart put together a Daily Show montage on the theme.

It’s Washington’s favorite sound bite these days. Last week, Senate Majority Leader Harry Reid, D‑Nev., even called for having “an adult conversation” about prostitution in Nevada (I’m pretty sure you can’t have any other kind).

There’s something cringe-inducing about this sort of rhetoric: It’s just shy of announcing that you’ve decided to put on your “big-boy pants.” One would like to think that, among adults, an “adult conversation” goes without saying. And, like “let me speak frankly, here,” the phrase smacks of an admission that, up till now, you were just shining us on.

Still, if being an adult requires acknowledging reality, taking responsibility, and living within your means, we’ve got a very long way to go on Capitol Hill, in the White House, and among the public at large.

A new survey released the same week as Obama’s press conference shows that, among the general public, “cutting government spending may be popular, but there is little appetite for cutting specific government programs.”

The Harris polling firm showed more than 5,000 adults a list of 20 categories of federal spending. There was majority support only for cutting six of them, “and these do not include the big ticket items that comprise most of the federal budget.”

What areas are Americans willing to cut? Foreign aid, the space program, subsidies to business, and welfare programs. From the perspective of the average middle-class voter, this is “other people’s money.”

Eighty percent of respondents opposed cuts to Social Security, 67 percent rejected cuts to health care, and more opposed defense cuts than favored them. Is it any wonder that so many alleged “austerity” plans leave these three categories — almost two-thirds of the federal budget — off the table?

The Harris poll shows that most Americans either don’t know, or are unwilling to accept, the fact that our budget crisis can’t be solved without major cuts in benefits to middle-class voters.

Interestingly, at the state level, where governors can’t print money and actually have to balance budgets, that disconnect is far less pronounced. Blue-state Republican governors like Wisconsin’s Scott Walker and New Jersey’s Chris Christie are surviving — and may well win — their fights with public employee unions.

At a state firefighters’ convention in Wildwood recently, Christie got lustily booed. He gave it right back: “For 20 years, governors have come into this room and lied to you, promised you benefits that they had no way of paying for.” I can understand why you feel deceived, he said, but “Why are you booing the first guy who came in here and told you the truth?”

As someone who grew up in New Jersey, I find it disorienting to hear a Garden State Republican talk like that. The few GOP governors of my youth were genteel WASPs who seemed to consider it gauche to mention cuts. I loved the place, but considered it the densest state in the union in more ways than one.

Yet today, most New Jersey voters aren’t booing: Only 27 percent have a positive view of teachers unions, and Christie’s popularity remains above 50 percent.

We’re far from an “adult conversation” at the federal level just yet. But Walker and Christie are showing that, when the pinch comes, such a conversation is possible.