Editor's note: Julian E. Zelizer is a professor of history and public affairs at Princeton University. He is the author of "Jimmy Carter," published by Times Books, and editor of a book assessing former President George W. Bush's administration, published by Princeton University Press.
Princeton, New Jersey (CNN) -- When U.S. District Court Judge Henry Hudson ruled that the mandate to purchase health insurance in the new law was unconstitutional, many people began looking to the Supreme Court for a final determination.
Supporters and opponents of President Obama's health care bill are speculating as to whether the highest court in the land might rule the president's signature measure unconstitutional.
But the truth is that a Supreme Court ruling along these lines, which is against the odds, is probably not the greatest threat that health care faces. Nor is outright repeal. As Americans become more familiar with the benefits of the program, Republicans will find it more difficult to attack health care outright. With all the discussion about constitutional challenge or congressional repeal, the more likely threat is that Republicans will gradually weaken the program to the point that it is ineffective.
Although the administration has liked to point out that programs such as Social Security started small and gradually expanded over time, it is worth noting that there are other programs, such as environmental regulations, that became weaker over time even when they remained on the books.
Since Ronald Reagan became president in 1980, Republicans learned it was more politically effective to undermine programs through funding cuts and administrative appointments than it was to mount outright challenges that aimed to dismantle public policies. When Republicans directly targeted benefits, such as Reagan's effort to cut Social Security benefits 1981 or the effort by the Republican Congress to reduce Medicare spending in 1995, they were burned.
So Republicans mastered an alternative strategy that has proven to be damaging to government programs. Instead of directly attacking programs, they have relied on more subtle mechanisms to scale back government. For example, both parties in Congress have found they can use the power of the purse as a weapon.
In several cases, conservatives have been able to prevent Congress from updating programs for many years. As a result, programs such as the minimum wage diminished in value.
Republicans have also gutted agencies so that they don't fulfill their missions. Reagan, for instance appointed James Watt as Secretary of Interior despite his staunch opposition to the policies he was responsible for. Assistant Secretary Housing and Urban Development Emanuel Savas, while on the job, wrote "Privatizing the Public Sector: How to Shrink Government."
The most striking example of this strategy has been environmental policy. Republicans have not had much success taking environmental policies off the books. Many middle-class Americans are supportive of the policies that have been put into place since the 1960s. But some Republicans who are not supportive of these regulations have been able to short-circuit the programs that are in place.
A case in point is the now famous Minerals Management Service which was responsible for overseeing offshore drilling. The Gulf oil crisis revealed that MMS had become an empty and corrupt shell by 2010. Scientists had been squeezed out of the decision making process. MMS allowed industry officials to complete their own inspection forms and officials received favors from the people they were regulating. When Obama took office he didn't do much to correct these problems, and the nation paid the price with the Gulf oil spill.
If the health care law remains in place, Republican opponents will turn to indirect attacks, if they follow the pattern set by conservatives since the 1970s. Because most of the benefits of health reform won't start until 2014, Republicans have an unusual amount of time in the implementation phase to mobilize against the program.
The most obvious line of attack will be on funding. House Republicans will propose appropriations that don't sufficiently fund key components of the program, such as Medicaid expansion, so that it cannot be implemented efficiently.
Republicans will also have the power to conduct hearings if they want to try to expose shortcomings in the law or stir up public opinion. Hearings have been effective in the past for both parties. During the 1970s, liberal Democrats sought to highlight the ways in which airline regulation did not benefit consumers. Senate hearings were used to dramatize their point by highlighting problems such as the mistreatment of pets in the shipping process.
As Professors Theda Skocpol (Harvard University) and Larry Jacobs (University of Minnesota) have argued in a fascinating paper for the Russell Sage Foundation, the health care program also remains vulnerable because the administration settled on health care exchanges that were run by the states rather than the federal government.
As a result, states controlled by Republicans governors will be able to weaken the administrative strength of the program and avoid enforcing many of its consumer protections.
Passing legislation was only one part of the battle for supporters of the health care law. Now comes an equally contentious stage -- the struggle over implementing the law. In many respects, the looming court battles over health care are the least of Obama's problems. The fight over implementation is where real challenge will lie for the program.
The opinions expressed in this commentary are solely those of Julian E. Zelizer.