About the authors
Julian Zelizer is a political historian at Princeton University and a fellow at the New America Foundation. He is the author of "The Fierce Urgency of Now: Lyndon Johnson, Congress, and the Battle for the Great Society."
Eric Patashnik is a professor of public policy and political science at Brown University.

There’s a reason programs such as Social Security are hard to kill, even for Republicans with the means to do so. (Bigstock)

While Donald Trump vowed during his presidential campaign not to govern like a tea party radical — “I’m not going to cut Social Security like every other Republican, and I’m not going to cut Medicare or Medicaid,” he vowed last year — his most recent Cabinet appointments suggest otherwise. The president-elect has been announcing picks who will most likely move hard right on the budget, just as top congressional Republicans such as House Speaker Paul D. Ryan (Wis.) want. At Health and Human Services, Rep. Tom Price (R-Ga.), a staunch critic of the Affordable Care Act and the traditional Medicare and Medicaid programs, is slated to be in charge of their implementation. Ben Carson, who has no experience with urban policy but has expressed radical positions on social safety net programs, may be heading the Department of Housing and Urban Development. And Chief of Staff Reince Priebus has been working closely with congressional Republicans who are determined to cut social spending significantly.

Thus there is reason to believe that the Trump administration, despite Trump’s campaign promises, could deliver on the longstanding conservative goals of not only repealing Obamacare (which Trump pledged to do) but also transforming Medicaid into block grants, turning Medicare into a “premium support” system (ending the program’s traditional open-ended commitment to pay for medical services) and sharply cutting funding for Great Society programs, including food stamps. “I’ve been working on these issues since 1972,” Robert Greenstein, the president of the Center on Budget and Policy Priorities, said in a recent interview. “This is by far the gravest threat to the safety net, and to low-income people, that I’ve seen in my close to half a century of working on these issues.”

But if Republicans pursue a retrenchment agenda, they will quickly learn that shredding the safety net is much harder than it seems.

Just as liberals in power often discover that it is difficult to expand the scope of government, conservatives in power have traditionally found that dismantling existing programs can be daunting even under favorable circumstances. This is perhaps why a seasoned politician such as Senate Majority Leader Mitch McConnell (R-Ky.) is already signaling his reluctance to push forward on restructuring health care for seniors, while House Minority Leader Nancy Pelosi (D-Calif.) is itching for a fight.

For a preview of what a revived Republican war on welfare might look like, conservatives who hope Trump’s win will usher in their budget-cutting agenda should consider what happened when Ronald Reagan was elected president in 1980 and Republicans gained control of the Senate. In contrast to 2016, that election created the perception that Reagan’s victory over President Jimmy Carter was a triumph for small government. Reagan, who cut his teeth in the conservative movement, appeared to have a mandate to undermine the discredited legacy of liberalism.

But when Reagan moved to dismantle the welfare state, he encountered tremendous resistance. In 1981, he pushed for a reduction in early retirement benefits in Social Security. Democrats pounced. Led by Speaker Tip O’Neill (Mass.), the Democrats mounted a furious campaign to paint Republicans as heartless and unfair. Rep. Claude Pepper (D-Fla.), the chairman of the Select Committee on Aging, termed the plan ”insidious” and ”cruel.” The campaign worked. Reagan backed down. When Reagan started talking about Medicare reform, Democrats counterpunched again. “I, for one,” O’Neill said, “am not going to stand by silently and let the Republicans add intolerable medical expenses to the budgets of millions of older Americans already struggling to get by.” As Paul Pierson has shown in a landmark study of the failure of Reagan and British Prime Minister Margaret Thatcher to claw back the welfare state, retrenchment is risky business for elected officials. It is one thing to attack Big Government in the abstract, and quite another to withdraw benefits from actual constituents.

Other Republicans have also seen their plans to cut the welfare state go down in flames. When President Dwight Eisenhower’s secretary of health, education and welfare, Oveta Culp Hobby, went after Social Security’s unique tax system with the support of Sen. Carl Curtis (R-Neb.), the program’s defenders stopped the plan in its tracks. Eisenhower ended up expanding Social Security coverage and wrote his brother that, “Should any political party attempt to abolish social security, unemployment insurance, and eliminate labor laws and farm program you would not hear of that party again in our political history.” When President George W. Bush tried to spend his “political capital” after the 2004 election by privatizing Social Security, with a Republican Congress to support him, the plan quickly fizzled despite a major public push by the White House.

Conservative assaults on public policy frequently trigger a political backlash among activists who were dormant until that moment, meaning they end up encountering resistance their instigators weren’t prepared for. Liberals, for instance, created groups such as the National Coalition for the Homeless to protect the interests of disadvantaged and marginalized Americans.

The Senate also provides a key line of defense for the welfare state. Unless Republicans employ the “nuclear option,” a parliamentary move that would empower a simple majority to limit or eliminate the filibuster, Senate Democrats still can use the filibuster to stymie proposals outside the budget reconciliation process. If McConnell ultimately signs on to the Medicare restructuring agenda, incoming Senate Minority Leader Charles E. Schumer (D-N.Y.) will be adept at using the procedural tools at his disposal to obstruct the bill’s progress. While Senate Democrats can no longer filibuster Cabinet appointments — a decision by Sen. Harry M. Reid (D-Nev.) that the party is probably coming to regret — the narrow Republican majority means that they have to pick off only a few members of the GOP to block a nomination, although there is little precedent for the Senate halting a Cabinet nomination on social policy grounds.

None of this is to say that President Obama’s legacy and many Great Society programs are not at serious risk. They are. Reagan’s era lacked a unified Republican Congress to work with, which we have now. And the Republican caucus today is also far more ideologically conservative than the Robert J. Dole GOP of the 1980s.

More worrying yet, Obamacare has not generated the broad support of programs such as Social Security. In a post-election poll, 45 percent of Americans had an unfavorable view of the ACA, and the low-income citizens who have gained the most under the law have not been mobilized into a robust constituency. While senior citizens jealously guard their Medicare benefits, the proposal to turn Medicare into a “premium-support” system is extremely complicated, creating strategic opportunities for the GOP to reduce the visibility of Medicare cutbacks and diffuse political accountability among voters. In sum, liberals should not assume the welfare state is invulnerable.

Democrats will need to marshal all of their political resources for coming battles over welfare. Not only will they need to activate the groups that have come to the defense of New Deal and Great Society programs in the past, but they will also need to do more to engage constituencies that have not yet come to the fore. This will mean highlighting the damage that dismantling programs will do to the lower- and middle-class voters Trump won in the election, clearly explaining the tangible benefits that already come from these policies, and doing the hard work of explaining how seemingly arcane moves, such as transforming programs into block grants, would erode entitlement protections. If they can accomplish all this, then, as Reagan learned, Democrats might just have a chance to hold back the rising Republican tide, giving them the chance to develop more effective and durable social policies for the 21st century.