Administration officials are coming forward with a grim compendium of jobs to be lost, services to be denied or delayed, military defenses to be let down and important operations to be disrupted. Obama’s new chief of staff, Denis McDonough, spoke of a “devastating list of horribles.”

For most Americans, though, it’s far from certain they will have a terrible, horrible, no good, very bad day if the budget-shredder known as the sequester comes to pass. Maybe they will, if the impasse drags on for months.

For now, there’s a whiff of the familiar in all the foreboding, harking back to the mid-1990s partial government shutdown, when officials said old people would go hungry, illegal immigrants would have the run of the of the land and veterans would go without meds. It didn’t happen.

For this episode, provisions are in place to preserve the most crucial services — and benefit checks. Furloughs of federal workers are at least a month away, breathing room for a political settlement if the will to achieve one is found. Many government contractors would continue to be paid with money previously approved.

But while the government prepares to make the best of a tough situation, it’s putting the worst possible face on it all.

Education Secretary Arne Duncan says teacher layoffs have already begun, but he has not backed up that claim and school administrators say no pink slips are expected before May, for the next school year, if thebudget crisis persists.

Interior Secretary Ken Salazar said the money crunch means the national parks system will be hit with a “perfect storm.”

But perish the thought of yellow police tape around Yellowstone. It’s far from settled that parks would close. Officials said to expect reduced operating hours, fewer rangers, bathrooms that might be locked and trash that might not be collected as often.

To be sure, the cuts are big and will have consequences. Knowing what they will be, though, is far from a precise exercise.

And there is a lot of improbable precision in administration statements about what could happen: more than 373,000 seriously ill people losing mental health services, 600,000 low-income pregnant women and new mothers losing food aid and nutrition education, 1,200 fewer inspections of dangerous work sites, 125,000 poor households going without vouchers, and much more.

“These numbers are just numbers thrown out into the thin air with no anchor, and I think they don’t provoke the outrage or concern that the Obama administration seeks,” said Paul Light, a New York University professor who specializes in the federal bureaucracy and budget. For all the dire warnings, he said, “It’s not clear who gets hurt by this.”

The estimates in many cases come from a simple calculation: Divide the proscribed spending cut by a program’s per-person spending to see how many beneficiaries may lose services or benefits under the sequester.

But in practice, through all the layers of bureaucracy and the everyday smoke and mirrors of the federalbudget, there is rarely a direct and measurable correlation between a federal dollar and its effect on the ground.

That has meant a lot of tenuous “could happen” warnings by the administration, not so much “will happen” evidence.

So it was in Health and Human Services Secretary Kathleen Sebelius’ letter to Congress laying out likely consequences of the spending cuts for her agency’s operations. She said the sequester “could” compromise the well-being of more than 373,000 people who “potentially” would not get needed mental health services, which in turn “could result” in more hospitalizations and homelessness.

Duncan left himself less wiggle room. “This stuff is real,” he said last week. “Schools are already starting to give teachers notices.”

Asked to provide backup for Duncan’s assertion, spokesman Daren Briscoe said it was based on “an unspecified call he was on with unnamed persons,” and the secretary might not be comfortable sharing details.

Briscoe referred queries about layoffs to the American Association of School Administrators. Noelle M. Ellerson, an assistant director of the organization, said Monday that in her many discussions with superintendents at the group’s just-completed annual meeting, she heard of no layoffs of teachers. While everyone is bracing for that possibility down the road, she said, “not a single one I spoke with had already issued pink slips.”

Most school district budgets for the next school year won’t be completed for two months, she said, meaning any layoff notices would come in early to mid-May. “No one had yet acted.”

As for the assertion that 600,000 women could be dropped from the Women, Infants and Children Program, that’s not to say the rolls would be cut by that number. The actual number is likely to include women who are not enrolled in the program now and could be denied when seeking to join it. Federal officials say the true number will depend on how states can manage their caseloads.

Transportation Secretary Ray LaHood has warned of impending furloughs of air traffic controllers, who may need to take one day off every two weeks, and said air-travel delays are likely across the country. Asked Friday why the airline lobby predicted no major impact on air travel from the sequester, he said, “I don’t think they have the information we’re presenting to them today.”

“The idea that we’re just doing this to create some kind of a horrific scare tactic is nonsense,” LaHood said. But it’s a pressure tactic nonetheless: “What I’m trying to do is to wake up members of the Congress on the Republican side to the idea that they need to come to the table.”

However the cuts fall, Light at NYU says the Washington Monument ploy, also known as the Firemen First principle, is at work.

It goes like this: Put someone’s budget at risk and the first thing you’ll hear is a threat to close a cherished national symbol or lay off firefighters and police, when in fact there are other ways to cut spending.

It so happens the Washington Monument is already closed, for earthquake repair. But Obama indulged in the Firemen First principle quite literally.

He appeared at the White House in front of officers in blue uniforms to warn of the consequences of the sequester. “Emergency responders like the ones who are here today — their ability to help communities respond to and recover from disasters will be degraded.”

FBI and Border Patrol furloughs are expected. Still, the White House has directed agencies to avoid cuts presenting “risks to life, safety or health” and to minimize harm to crucial services.

The law gives little flexibility to agencies to protect favored programs, except for big ones specifically exempted from the automatic cuts, such as Social Security, Medicare, Medicaid and veterans benefits. There’s only so much latitude to move money among accounts.

But not everything is cast in stone. The Small Business Administration, for example, should be able to avoid furloughs because of early retirements already achieved, said Karen Mills, the administrator. And she said declining demand for one type of loan should free up money for other lending, so “we are not slowing down giving loans to anyone.”

In the partial government shutdown during his presidency, Bill Clinton and his officials told some tall tales and sketched dark scenarios that didn’t come to pass, though some might have if the crisis had lasted weeks or months longer. The shutdown played out over two installments totaling 26 days from mid-November 1995 to early January 1996.

National park properties closed (yes, even the Washington Monument), passport and federal mortgage insurance processing were disrupted and toxic waste cleanup stalled as hundreds of thousands of federal workers went idle, paid retroactively later. But states, communities and private groups stepped up to tide over the neediest, keeping Meals on Wheels rolling with their own resources, for example, until Clinton found emergency money to cover the costs. Warnings that Medicare treatment would be withheld proved unfounded, and veterans got their care.

Contractors, who perform many key services for government, kept working for IOUs. A claim by the government that deportations “have virtually ended” was not so.

The Justice Department told the story of a Florida gas station rejecting the government-issued credit card of a drug-enforcement agent to illustrate the indignity of it all.

But the reality was humdrum: The card had merely expired.