Washington ? Barack Obama promises $4,000 credits to help pay college tuition. Hillary Rodham Clinton backs $25 billion for home heating subsidies. And John McCain wants to not only extend President Bush’s tax cuts, but eliminate the alternative minimum tax at a cost of about $2 trillion over 10 years.

Then there’s reality.

These campaign pledges – and dozens more in the manifestos of the leading presidential candidates – face a collision with the real world come January, when the new president will start putting together a real budget and economic plan, one drafted against the backdrop of record federal deficits exceeding $400 billion. Even more challenging is the growth of the Medicare and Social Security retirement programs, which budget experts say could require wrenching benefit cuts, politically difficult tax hikes or both to handle the retirement of the baby boom generation.

In that environment, promises to effectively rebate the first $500 of Social Security payroll taxes (Obama), provide $1,000 tax credits for retirement savings (Clinton) or cut the corporate income tax by 10 percentage points (McCain) may turn out to be campaign fantasies.

“They’re operating in Never Never Land. … None of them are honestly addressing the real challenges that they’re going to be facing if they’re elected,” said Leon Panetta, former budget director and chief of staff for President Clinton. “We’re facing a deficit bubble that is getting increasingly worse and at some point is going to explode on us.”

Plans don’t add up

For now, the campaigns are sticking with policy papers that don’t add up but cater to political constituencies.

Obama’s “Keeping America’s Promise” manifesto is full of costly prescriptions for the economy. Obama proposes tax cuts for senior citizens and college students, and $500 for every wage-earner, totaling $80 billion to $85 billion a year. He says he would pay for the tax cuts by closing loopholes and closing offshore tax havens, but those steps would fall far short of fully offsetting their costs.

Both Obama and Clinton would keep in place many of the Bush tax cuts, including rate cuts for most taxpayers and the $1,000 per child tax credit. Both would let rate cuts for upper-income taxpayers expire, and use the savings to help pay for their health care promises.

To address looming shortfalls in Social Security, Obama supports raising the cap that limits the 6.2 percent Social Security payroll tax to the first $102,000 of income.

Obama also promises a $60 billion investment in infrastructure and an $18 billion per year boost in education spending. The Illinois senator says his plan to withdraw U.S. forces from Iraq will generate savings to help pay for these items, but that doesn’t qualify as an offset under budget rules because the Iraq spending is an emergency expense, not a permanent part of the budget.

McCain’s tax shift

For his part, McCain voted against Bush’s tax cuts as tilted too much in favor of the wealthy. He has since changed his mind.

Now, with most budget experts forecasting deep deficits for the future, McCain wants to extend the Bush tax cuts, which expire at the end of 2010. The price tag for McCain’s plan would soon exceed $300 billion a year after government borrowing costs are factored in.

McCain also wants to eliminate the alternative minimum tax, or AMT, which would add more than $2 trillion in accumulated deficits to the federal ledger from 2010-2020. The AMT was enacted in 1969 to make sure the wealthy paid at least some tax, but now also threatens about 20 million additional taxpayers with levies averaging $2,000 if annual fixes aren’t renewed.

Clinton’s campaign generally succeeds more than the others at providing offsets – revenue increases or spending cuts – to finance programs such as her plan to provide health care for all.

But even if the next president “pays for” new initiatives, they will still be left with an underlying budget deficit exceeding $400 billion and the looming crises in Social Security, Medicare and the Medicaid health care program for the poor and disabled.

Even so, Clinton campaign literature promises a “return to fiscal responsibility. After six and a half years of Bush’s fiscal irresponsibility, Hillary wants America to regain control of its destiny. She will move back toward a balanced budget and surpluses.”

Just how Clinton – or any of her rivals – might miraculously produce a budget surplus is not answered.