Despite what you might have heard, the coming battle on Capitol Hill is not really about “government spending” in the abstract. It’s about two radically different visions of how money should be spent.

Republicans who feign attacks of the vapors and fainting spells over the big, scary deficit would be more convincing if they didn’t begin with the insane premise that defense spending should be sacrosanct. The House leadership in the last few days has begun to signal retreat from this indefensible position, but it’s unclear how much of the hyperconservative GOP majority will follow.

Majority Leader Eric Cantor said Sunday that “every dollar should be on the table” — meaning that the Pentagon, which consumes nearly one-fourth of the entire federal budget, should be open to scrutiny as well. But this is a departure from last year’s Republican campaign pledge to solve the nation’s budget woes by cutting “discretionary” spending only, leaving intact the defense spending needed to “keep America strong.”

The Republican “Pledge to America” promised to cut “at least $100 billion in the first year alone,” notwithstanding “exceptions for seniors, veterans and our troops.” This was never a serious proposal, given that defense, entitlements and other mandatory spending consume about four-fifths of the budget. But it was a nice round number that sounded good.

Apparently it was music to the ears of some of the small-government Republicans — perhaps they should be called no-government Republicans — in the House majority, because they are pressing the leadership to make good on this reckless promise. According to The Washington Post, affected agencies would suffer a 30 percent cut in funding over the next seven months.

Do Americans really want the effectiveness of, say, food safety inspection to be eroded by 30 percent? What about air traffic control? I didn’t think so.

This would be just the beginning, however, if the Republican Study Committee — a conservative bloc that includes most House Republicans — were to have its way. This group proposes even deeper cuts, with nondefense agencies having to reduce spending by more than 40 percent over the next decade. They call their proposal the Spending Reduction Act, but if we weren’t in a new era of polite discourse I’d call it the Pro-Salmonella Act.

House Speaker John Boehner and the rest of the leadership must realize that this is sheer fantasy. They may even understand that while it is vital to bring the government’s revenues and outlays back into balance, moving too quickly would damage the fragile economic recovery. With President Barack Obama now focused on jobs, it will hardly help the GOP’s prospects in 2012 for the party to be perceived as anti-jobs.

But will the leadership be able to bring hard-line conservatives along? The Study Committee’s Spending Reduction Act doesn’t give an inch on Pentagon spending, even though Defense Secretary Robert Gates, of all people, is advocating $78 billion in cuts. But the conservative plan does propose eliminating a long list of specific subsidies and programs — and the list is about politics, not economics.

The conservatives want to end funding for the Corporation for Public Broadcasting, the Legal Services Corp., the National Endowment for the Arts, the National Endowment for the Humanities, the Energy Star program, the United Nations’ Intergovernmental Panel on Climate Change … you get the picture. Put together, these expenditures would not begin to pay for, say, the $13 billion Marine Corps landing craft that Gates plans to kill because we are no longer fighting World War II.

You’d think that Rep. Howard P. “Buck” McKeon, the new chairman of the House Armed Services Committee, would have applauded Gates’ frugality. Instead, he described himself as “not happy” and vowed he will “not stand idly by and watch the White House gut defense when Americans are deployed in harm’s way.”

In other words, it’s perfectly fine to waste money on defense. What’s not acceptable to GOP conservatives, apparently, is spending on agencies or programs that they oppose philosophically. Don’t believe in climate change, despite wide scientific consensus that it’s real? Just cut off funding for the U.N. panel that disagrees with your view.

It seems to have dawned on Cantor that this position is fundamentally untenable and politically unwise. He has his work cut out for him if much of the GOP caucus sees the budget as an expression not of policy but of vengeance and spite.

Eugene Robinson’s e-mail address is eugenerobinson(at)washpost.com.