In March 1964, President Lyndon B. Johnson vowed his administration would fight to pass a program of medical assistance for elderly Americans. “If not this week,” he pledged, “if not this month, if not this year, [then at] the earliest possible date.”

Nearly 20 years had passed since President Harry S. Truman first called for a national program to guarantee health coverage for all Americans. When Johnson finally signed the Medicare and Medicaid Bill on July 30, 1965, he declared, “We marvel not simply at the passage of this bill, but that it took so many years.”

Yet despite the lengthy fight, the new program offered near-immediate benefits to elderly Americans. The year before Medicare became law, only about one in four seniors was fully covered in a hospital emergency or for other extensive medical treatment. Medicare changed that. For the first time in U.S. history, seniors could count on receiving all necessary treatment without worrying about burdening their children with massive medical bills.

This year, President Barack Obama and Democrats in Congress built on Medicare’s promise of affordable, accessible medical care. With the Affordable Care Act, they extended to Americans of all ages the ability to receive needed care.

This legislative victory was more than 60 years in the making. From the day Truman proposed reform to the day Obama signed the Affordable Care Act into law, seven presidents tried, and failed, to fix America’s broken health care system.

There were some notable successes along the way — particularly the creation of Medicare — but those successes were tempered by the continuing struggles of tens of millions of uninsured Americans.

In large part, the difficultly of passing reform can be traced to Republicans, who consistently acted on behalf of insurance companies and other special interests to derail substantive change. As time passed, Republicans’ opposition to reform became even more entrenched. Though many Republicans had joined with Democrats to pass the Medicare and Medicaid Bill of 1965, not a single Republican voted for the Affordable Care Act.

The Affordable Care Act ends the insurance industry’s worst practices, guaranteeing that no American is denied insurance because of a pre-existing condition or is denied coverage for care when they get sick. It holds insurance companies accountable, prevents unjustified rate hikes and outlaws caps on annual and lifetime coverage. It reduces Americans’ premiums and out-of-pocket expenses, and extends new tax cuts to businesses, to help them cover the cost of insuring workers, making heath care more affordable for families and small businesses alike. It can create new quality, affordable coverage options for uninsured Americans.

Tim Kaine, former governor of Virginia, is the chairman of the Democratic National Committee. He can be e-mailed through the committee’s website at http://www.democrats.org/contact.html