Reducing government deficits Mitt Romney's way would mean less money for health care for the poor and disabled, and big cuts to nuts-and-bolts functions such as food inspection, border security and education.
Romney also promises budget increases for the Pentagon, above those sought by some Republican defense hawks, meaning that the rest of the government would have to shrink even more. Nonmilitary programs would incur still larger cuts than those called for in the tightfisted GOP budget plan that the House passed last month.
Differences over the government's budget and spiraling deficits are among the starkest that separate Republican challenger Romney and Democratic President Obama.
The two are almost certain to face off in November. Obama is sure to reach the 2,778 delegates he needs to secure his party's nod for a second time when five states, including New York, vote Tuesday. Romney is not far behind.
Obama's budget generally avoids risk, with minimal cuts to rapidly growing health care programs such as Medicare and Medicaid while socking wealthier people with tax increases. It's all part of an effort to close trillion-dollar-plus deficits.
Romney, by contrast, proposes broad cuts in government spending, possibly overpromising on reductions that even a Congress stuffed with conservatives might find hard to deliver.
His campaign materials give relatively few specifics, other than a pledge to bring total government spending down to 20 percent of the U.S. economy by the end of a first term in 2016.
Estimates by the nonpartisan Congressional Budget Office put current government spending at $3.6 trillion, or about 23.5 percent of the gross domestic product this year, slipping to 21.8 percent by 2016.
The math can get fuzzy. But the Romney campaign says that it needs to come up with $500 billion in cuts in 2016, the target year. Overall, Romney promises to shrink government spending by about one-seventh.
The GOP front-runner suggests raising the Social Security retirement age and reducing cost-of-living increases for better-off retirees.
He generally endorses a plan by House Budget Committee Chairman Paul D. Ryan, R-Wis., to gradually transform Medicare from a program that directly pays hospital and doctor bills into vouchers for subsidizing future beneficiaries in buying health insurance.
Because Romney promises to protect current Social Security and Medicare recipients from cuts, he could not get much savings from those programs by 2016. Combined, they are projected to make up about 44 percent of the budget that year. Interest costs, which cannot be touched, would make up an additional 9 percent of the budget, while Romney promises to add almost $100 billion to the Pentagon budget that year.
So what's left to cut?
*Medicaid -- The program now provides health care for about 50 million mostly poor and disabled people, including nursing home care for 7 in 10 patients nationwide. Obama's health care law sharply would boost Medicaid enrollment to cover more people above the poverty line, a move that Romney promises to repeal.
Like House Republicans, Romney promises to transform Medicaid into block grants for states and shed federal supervision of it. He would cap the program's annual growth to inflation plus a percentage point. His campaign says the approach would unshackle states to innovate and, by the end of a decade, cut costs by more than $200 billion a year.
Advocates for the poor say the inevitable result will be that millions of people would be bounced from the program. An Urban Institute study last year estimated that Ryan's cuts would force 14 million to 27 million people off of Medicaid by 2021. Romney's budget would make deeper cuts.
*Domestic agency budgets -- If Social Security is mostly off the table and current Medicare beneficiaries are protected, domestic Cabinet agency budgets would take a major hit in ways that could fundamentally alter government. The future growth of those discretionary programs funded through annual appropriations bills already was cut greatly in last year's deal to raise the government's borrowing limit.
At issue are these programs, just to name a few: health research; NASA; transportation; homeland security; education; food inspection; housing and heating subsidies for the poor; food aid for pregnant women; the FBI; grants to local governments; national parks; and health care for veterans.
Romney promises immediately to cut them by 5 percent. But they would have to be cut more than 20 percent to meet his overall budget goals, assuming health care for veterans is exempted. It's almost unthinkable that lawmakers would go along with cuts of such magnitude for air traffic control and food inspection or to agencies like NASA, the FBI, Border Patrol and the Centers for Disease Control and Prevention.
"It's just not sustainable," said GOP lobbyist Jim Dyer, a former staff director for the House Appropriations Committee. "What do you want to do with the national parks? Which ones do you want to close? The only way it adds up is if you go after the big, popular stuff, and nobody talks about that now."
Among the few specific cuts listed in Romney's campaign materials are proposals to cut the federal workforce by 10 percent through attrition, eliminate federal family planning money, privatize the money-losing Amtrak system and trim foreign aid.
*Other benefit programs -- Like Ryan's budget, the Romney plan would also cut benefit programs other than Social Security and Medicare. They include food stamps, school lunches, crop subsidies, Supplemental Security Income for very poor seniors and disabled people, unemployment insurance, veterans' pensions and refundable tax credits to the working poor.
Based on the Romney materials, it's impossible to project the size of the cuts to such programs. Suffice it to say, they would be controversial.
"There's good reason why Ryan's budget and the Romney budget don't have details," said Jim Horney, a budget analyst with the liberal-leaning Center on Budget and Policy priorities think tank. "If people knew what it would actually have to be done to accomplish what they're saying should be done, it's hard to imagine there would be widespread support for it."