When it comes to the budget, Mitt Romney, Newt Gingrich and Ron Paul all want to cut spending.

NEW YORK (CNNMoney) -- For all their differences, the 2012 Republican contenders have at least one thing in common: They all want to cut spending.

Rick Santorum wants to cut $5 trillion over 5 years, immediately return non-defense discretionary spending to 2008 levels, pass a balanced budget amendment and cap federal spending at 18% of Gross Domestic Product.









Mitt Romney would cap spending at 20% of GDP, immediately reduce non-security discretionary accounts by 5% and pursue a balanced budget amendment.

Newt Gingrich, Rick Perry and Jon Huntsman have designs of their own.

Problem is, the candidates lack a set of realistic, specific proposals that stand even a small chance of becoming law.

"If you look at most politicians talking about cuts, they are very, very, very short on specifics with a few exceptions," said Tad DeHaven, a budget analyst at the CATO Institute, a libertarian think tank that advocates for smaller government.

On the hunt for specific budget cuts, DeHaven combed through the economic plans listed on each candidate's campaign website.

He came away disappointed -- with one exception.

"From a spending standpoint, there is Ron Paul and then everybody else," DeHaven said. "You have a complete budget from Paul, and not much from anybody else."

Paul's plan doesn't lack ambition. He wants to eliminate the Departments of Energy, Housing and Urban Development, Commerce, Interior and Education.

And on his website, Paul lays out a four-year plan with budget lines for federal agencies and programs that he wants to eliminate with a high degree of specificity.

By way of contrast, Romney and Santorum list only a few programs they want to axe, despite their big promises.

Romney wants to cut funding for relatively small programs like Amtrak, the National Endowment for the Arts, foreign aid, the Corporation for Public Broadcasting and Title X family planning.

He does detail a few bigger ticket items, like a reduction in the size of the federal workforce and a modification to Medicaid that would turn it into a block grant program -- but not much else.

Overall, DeHaven said Romney's specific cuts are "tiny" and "the typical small stuff."

Santorum doesn't fare much better, focusing on red-meat Republican priorities like funding cuts for the National Labor Relations Board, USAID, Planned Parenthood and the Environmental Protection Agency.

The mix of politics and budgeting isn't too surprising, especially given that the candidates are still battling the Republican nomination, a process that requires capturing the attention of the conservative party base.

DeHaven said another factor is contributing to the lack of details: candidates from both parties often shy away from discussing budget cuts for fear of a backlash from interest groups and advocates.

"When you call for specific cuts, every program has a constituency, and that's when they come alive," DeHaven said.

For that reason, GOP candidates are returning to an old standby this cycle: The balanced budget amendment, a proposal that -- barring a GOP landslide in congressional races -- stands little chance of becoming law.

"Most candidates embrace a [balanced budget amendment] because they don't have the desire or ability to formulate a concrete proposal," DeHaven said.

Should one of the Republican candidates defeat President Obama in November, they will run up against another budget plan buzzsaw: Congress.

House Republicans, including an enthusiastic set of freshmen, devoted much of the 2011 legislative session to initiatives that would have reduced spending.

The House passed an ambitious budget that was never enacted, and funding for the federal government almost lapsed on a few occasions while lawmakers squabbled over relatively small budget cuts.

And in perhaps the best example of how difficult it can be to cut spending, the country was brought to the brink of default after negotiations over the debt ceiling dragged until the last minute.

At the termination of that debate, a large number of spending cuts were left to the super committee to identify. Why? Because lawmakers couldn't agree on specific programs to cut.

And of course, the super committee then failed at the same task, despite overwhelming pressure and an extended deadline.