In the presidential debates, Barack Obama and Mitt Romney ranged across dozens of topics, but an important one didn't come up: federalism. And no wonder.
The idea that the Constitution grants only limited and enumerated powers and leaves the remainder to the states is foreign to those who believe that the national government should or even could address voters' every concern. But contrary to the view widely shared by the political class, Washington—in particular, Congress—does not have the power to pass any law it wants in the name of the "general welfare."
Politicians should take heed. Voters are increasingly focused on the proper role of government in society: Witness the rise of the tea party and unease over the massive debt caused by entitlements and other government handouts. The continuing loud objection to ObamaCare's takeover of health care shows that voters want to preserve the Constitution's architecture of limited federal power.
Keeping the federal government within its proper constitutional sphere is critical to all Americans, regardless of their political allegiance. This is because federalism is not about protecting "states' rights" but about preserving individual liberty. In the words of a unanimous 2011 Supreme Court decision, Bond v. United States, by "denying any one government complete jurisdiction over all the concerns of public life, federalism protects the liberty of the individual from arbitrary power. When government acts in excess of its lawful powers, that liberty is at stake."
Federalism also allows states to craft policies that best suit the preferences and needs of their citizens, who can always vote with their feet. Likewise, leaving key policy choices to state governments benefits voters through sheer proximity to decision makers. State legislators are often part-timers who work and live in our communities and are more palpably accountable to us.
State-level reform thus comes more swiftly and better reflects the desires of ordinary constituents. States in recent years have led the way in reforming welfare, health care, education and regulatory policies. They have cut deficits, balanced budgets, reformed tax codes and produced jobs.
Federalism also benefits the national government. By having up to 50 different approaches to an issue, Congress can see what works.
Despite federalism's many virtues, it is not much in vogue. Democrats view it as a quaint, 18th-century relic, another disposable constitutional concept that stands in the way of "progress." The Obama administration has been particularly disdainful of federalism, with ObamaCare unconstitutionally coercing states into fundamentally revising their Medicaid programs and compelling individuals—under the guise of regulating interstate commerce—to buy a government-approved health-insurance policy.
Republicans pay lip service to federalism but too often toss it aside to achieve their own policy goals. For example, many congressional Republicans, concerned about abusive lawsuits, would nationalize many aspects of medical malpractice, an area of law traditionally reserved to the states.
Meanwhile big-spending states such as California and Illinois have been lobbying Congress for a federal bailout of their unfunded pensions. From the federalist perspective, it is appropriate that the promiscuous spending of some states makes it difficult for them to borrow more money. Such consequences, while dire, provide the political leverage that citizens living within those states need to force their elected representatives to reform.
Yet Washington may well end up rescuing these nearly bankrupt states—because some states will compromise their own sovereignty when the price is right, and the federal government is only too happy to take over and claim political credit. For there is no more assiduous underminer of federalism than the federal government itself. Every session of Congress and every administration adds to the existing voluminous body of federal law that continues to federalize wide swaths of traditional state authority. This must stop.
There was one glimmer of hope for federalism in the third presidential debate, when Mitt Romney talked about saving Medicaid by making block grants to states. "We'll take that health-care program for the poor and we give it to the states to run because states run these programs more efficiently," he said. "As a governor, I thought please, give me this program. I can run this more efficiently than the federal government and states, by the way, are proving it."
If Mr. Romney succeeds in his race for the White House, let's hope he doesn't forget that states can be trusted to run their own affairs.
Mr. Rivkin served in the Justice Department under Presidents Reagan and George H.W. Bush and represented 26 states in challenging ObamaCare. He has advised the Romney campaign.
Ms. Foley is a law professor at Florida International University College of Law and author of "The Tea Party: Three Principles" (Cambridge, 2011).