Pain has no political constituency.

This fundamental rule of American politics (and democratic systems more generally) points up the difficulty of enacting or sustaining public policies that leave large numbers of citizens worse off. Politicians dread casting votes on legislation that will impose costs on any significant group of constituents, lest the opposition seize on the issue in the next election. Austerity policies typically spell defeat for the political party or coalition that imposes them (see Greece). Given the political consequences of inflicting pain, many of the key budget prescriptions embodied in the budget plan developed by Representative Paul Ryan and now effectively endorsed by Mitt Romney will never be realized in practice.

Political parties that run on a “cod liver oil” platform face a critical obstacle on the campaign trail. They can always be undersold in the competition for votes by other parties that offer voters instead the proverbial spoonful of sugar. The political challenge entailed by recommending policies that promise pain becomes more acute if the danger that the pain is designed to avert lies far off in the future.

In 1984, Democratic presidential nominee Walter Mondale vividly demonstrated the lesson that pain is a losing political proposition. He believed that the American people would accept the hard truth that tax increases were the only solution to the large federal deficit generated by the tax cuts pushed through by the Reagan administration. In his acceptance speech at the Democratic convention, he delivered the bad news directly:

“Whoever is inaugurated in January, the American people will have to pay Mr. Reagan’s bills. The budget will be squeezed. Taxes will go up….Mr. Reagan will raise taxes, and so will I. He won’t tell you. I just did.”

Mondale’s candor earned him no credit among the American people. With barely 40 per cent of the popular vote, he lost 49 states. (If Reagan had decided to campaign in Minnesota, Mondale’s home state, the Democrat might have lost all fifty.)

Another episode from the Reagan era demonstrates a more palatable approach to allocating pain. In 1981, recognizing that Social Security would soon face a short-term funding shortfall, Reagan appointed a bipartisan group, the National Commission on Social Security Reform (called the Greenspan Commission after its chair, Alan Greenspan) to review the program and its finances. The commission recommended a series of changes that included increased taxes and reduced benefits. Congress in 1983 approved recommendations that yielded $168bn to assure that the program would remain solvent. The solution set borrowed from both parties, including increasing in the retirement age and raising the payroll tax ceiling on higher income workers. Importantly, the commission gave both parties political cover, and the bipartisan support effectively removed the issue from the 1984 campaign.

But the conditions that made possible the 1983 compromise have proven harder to replicate over time. Barack Obama sought to lay the groundwork for a similar bipartisan approach when he appointed the National Commission on Fiscal Responsibility and Reform (usually referred to after its co-chairs as Simpson-Bowles). Rather than embrace the report, however, lawmakers in both parties shunned it. Among the obstacles were a more sharply polarized political context and the lack of urgency inherent in the underlying problem. Any long-term debt crisis involves a distant threat, quite unlike the immediate problems facing Social Security in the early 1980s.

If we apply the lessons from these episodes to the Ryan budget, certain conclusions follow. First, so long as the Democrats control one of the main policy branches of the national government (the White House, the Senate, or the House), the plan will go nowhere. Indeed, that is the best of all worlds for the GOP, because then Republicans don’t have to answer for the consequences. Second, were the Republicans to sweep the 2012 elections, they might enact the features of the plan attractive to their core constituents — cutting discretionary expenditures for the poor and lowering taxes. The result would be a larger federal deficit and a worsening of the future debt problem. Third, Republican lawmakers would likely defer proposed changes in Medicare and changes in the tax code (such as eliminating popular deductions) intended to offset tax cuts. These unpopular moves would leave them politically vulnerable in 2014. To enact them could spell a quick farewell to majority status for the GOP.

Republicans know this. Many are already scared to run on the Ryan scheme to replace traditional Medicare for those under the age of 55 with vouchers that cannot possibly cover the same level of services. That Medicare poses a danger to the federal government’s solvency as baby boomers retire may be true, but proposing to slash Medicare spending still makes for bad politics. (And the Republican ticket appreciates the politics, too, witness the Romney-Ryan attack on Obamacare for allegedly cutting Medicare.) Nor will the Republicans’ Orwellian efforts to package the reform as a plan to protect and enhance Medicare work. In a contested information environment, efforts to reframe the terms of debate don’t work.

The same holds for the unspecified revenue increases that the Ryan plan expects to realize from reforming the tax code. At a time when the federal government already takes in much less than it spends, the GOP budget formula seeks lower tax rates and an end to taxes on capital gains. The plan in its pure form offers more than $4trn in tax cuts over the next decade. Finding the revenue to offset such a loss runs afoul of political reality at every turn. End the home mortgage interest deduction? The one for state and local taxes? How about putting a stop to charitable deductions? These moves amount to political suicide. Yet nothing less could close the gap between revenues and expenditures entailed by the Ryan budget (or the Romney tax plan proposed during the primaries).

In the end, then, the politics of pain mean that anything resembling the Ryan-Romney budget approach will become another exercise in supply-side economics — the discredited faith that cutting taxes sharply enough will generate so much economic growth that total revenues will increase. The Republicans can deliver the tax cuts and some spending reductions targeted at the most vulnerable, who are also the least organized and powerful in our politics. But for those who think the Ryan budget represents a serious approach to the long-term federal debt problem, believing in the tooth fairy is a better bet.

Andrew Polsky is Professor of Political Science at Hunter College and the CUNY Graduate Center. A former editor of the journal Polity, his most recent book is Elusive Victories: The American Presidency at War. This post originally appeared on the OUP blog here.