This week, the Supreme Court will hear lawsuits challenging the constitutionality of the Affordable Care Act, the historic health care reform bill that President Barack Obama signed into law in March 2010.

The law provides valuable benefits to American families: It will give 93 percent of Americans access to affordable health care coverage that can never be taken away; protect consumers against insurance company abuses; make unprecedented investments in prevention, wellness and quality of care; aggressively control runaway health care spending; lower health care costs for small businesses; and transform the health care delivery system to significantly improve the health of the American people.

While many reforms will kick in over the next few years, the law has already banned lifetime limits on health insurance benefits for more than 100 million Americans, prohibited insurers from canceling coverage when you get sick, provided preventive care without co-pays for more than 80 million Americans (including all Medicare beneficiaries) and allowed 2.5 million young adults to stay on their parents’ health care plans until they turn 26.

During the law’s drafting and debate, my colleagues and I diligently sought the participation and support of our Republican counterparts. In the committee I am chairman of, we accepted 161 Republican amendments. Unfortunately, common sense bowed to ideology: Congressional Republicans declared a strategy to make health care reform the president’s “Waterloo” and voted unanimously against the bill.

Having failed in Congress to take health insurance away from millions of Americans and put insurance companies back in control, Republicans are counting on the courts to undo our progress. The leaders of this effort are working from a time-honored script: Every reform in history that has sought to expand the prosperity and rights of the American people has been subjected to well-funded, but futile, legal attacks. Opponents of the New Deal, Social Security, the Civil Rights Act and the Voting Rights Act sought to weaken our country through precisely such a strategy. They failed then, and they will fail now.

On the legal merits, the law’s opponents are flat wrong. Today, health care constitutes one-sixth of the economy. It is simply absurd to suggest that in the 21st century the federal government, exercising its authority under the Commerce Clause, cannot make laws affecting an area that is so clearly commerce. As Harvey Wilkinson, a 4th Circuit judge appointed by President Ronald Reagan, noted, “The idea that Congress is constitutionally disabled” from regulating one-sixth of the economy “is a heavy judicial lift.”

Recognizing the futility of such an argument, opponents expect the court to ignore a century of judicial precedent and strike down the individual responsibility provision, which requires everyone who can afford it to purchase health insurance or pay a penalty, starting in 2014. The majority of Americans who already have insurance will not be affected by this provision at all.

Opponents argue that those who choose not to purchase health insurance do not engage in commerce and thus are beyond Congress’ power. However, as 6th Circuit Court of Appeals Judge Jeffrey Sutton, appointed by President George W. Bush, wrote in upholding the law’s constitutionality: “Faced with $43 billion in uncompensated care, Congress reasonably could require all covered individuals to pay for health care now so that money would be available later to pay for all care as the need arises. … No one is inactive when deciding how to pay for health care, as self-insurance and private insurance are two forms of action for addressing the same risk. Each requires affirmative choices; one is no less active than the other; and both affect commerce.”

Every American will need health care at some point — even if only at the end of life. As Reagan appointee Judge Laurence Silberman recently wrote, Congress has the power to “forge national solutions to national problems, no matter how local — or seemingly passive — their individual origins.”

By bringing everyone into the system, the law makes health care fairer, cheaper and, most importantly, available to everyone regardless of age or health status.

This last point — the fact that the law makes health care available to everyone regardless of age or health status, including those with pre-existing conditions — is something the law’s opponents don’t talk much about in public, and it’s obvious why. If the court strikes down the requirement that everyone get insured, the law’s provision requiring insurers to offer coverage to everybody will also fall. The political attack dogs seeking to undo this law want to send us back to the bad old days, leaving tens of millions uninsured, including many with pre-existing conditions, shifting costs to those who have insurance and allowing insurance companies to raise premiums unchecked.

Many of the states suing to overturn the law are among those whose citizens will benefit most from its reforms. There could not be clearer proof that the real motivation for these lawsuits is political. We must not let the oldest, basest politics stand in the way of improving health care for American families.

It’s time to turn the page on the battles of the past, protect the progress we have made and move forward to deliver on the promise of access to health care not only for the healthy and wealthy but for all Americans.

Sen. Tom Harkin (D-Iowa) is chairman of the Health, Education, Labor and Pensions Committee and of the Appropriations Subcommittee on Labor, Health and Human Services, and Education.