The Supreme Court was ideologically split but trending decidedly conservative: It routinely struck down expansive government programs passed by state legislatures and an emboldened Democratic Congress.

The game-changing Democratic president was determined to reimagine the federal government and have it play a more active role in the lives of suffering Americans.

The program under the high court’s microscope was unprecedented in scope and revolutionary in concept, providing a national safety net that was argued to be far outside the constitutional boundary of the federal government’s powers.

Today, there are unmistakable comparisons to the court’s action on the Social Security Act of 1935 as the current justices consider whether to accept a constitutional challenge of the 2010 Affordable Care Act. A decision could come as early as Monday morning.

“This was a new untested area of federal authority and it was inevitable that it would be challenged in the courts,” Social Security Administration historian Larry DeWitt writes on the agency’s Web site.

“No one could be sure that the nascent Social Security Act would survive its infancy,” he wrote.

Victory came in three separate cases, all decided by the court on May 24, 1937. It is no surprise that the administration and those who support the health-care act have attempted to link the current challenges to the ones that faced a program that now is a touchstone of American life.

“Throughout history, there have been similar challenges to other landmark legislation, such as the Social Security Act, the Civil Rights Act and the Voting Rights Act and all of those challenges failed,” the Justice Department said in a statement in September when it asked the justices to consider the health-care act.

But there is an answer to the obvious question of why the health-care act might not be constitutional while Social Security — and its offshoot Medicare — are. They were built on separate constitutional powers.

Congress contends that its ability to require almost all individuals to buy health insurance or pay a fine comes from its power to regulate interstate commerce and enact laws “necessary and proper” to carry out the goals of the federal government.

Social Security, on the other hand, was justified under Congress’s power to levy taxes and spend money “to provide for the general welfare.”

What that open-ended wording means is an argument as old as the union.

James Madison thought it meant that the federal government could raise and spend money only for those purposes spelled out in the Constitution. Alexander Hamilton said it was much broader and gave the government wider latitude to provide services that improved Americans’ general welfare.

The Hamiltonian view gradually gained ground, but it was no certainty that the Supreme Court of the 1930s was ready to continue to embrace it when it came to the expansive programs of the New Deal. It rejected a federal program of agricultural price supports and controls that Congress had justified under the same taxing powers.

That in turn led to President Franklin D. Roosevelt’s ill-advised and eventually unsuccessful “court-packing” proposal that would have allowed him to shift the court’s balance by adding justices of his choosing.

It turned out not to be necessary in the case of Social Security. Justice Benjamin N. Cardozo, writing for a seven-justice majority, declared in Helvering v. Davis that the intellectual battle between Madison and Hamilton was over, and that Hamilton had won.

The “concept of the general welfare” is not static, he said. “Needs that were narrow or parochial a century ago may be interwoven in our day with the well-being of the nation. What is critical or urgent changes with the times.”

He said that only a system of old-age benefits that were national, rather than different by state, would serve the day’s needs.

Such logic leads to an interesting agreement between both sides of the battle over the health-care act: that a single-payer health-care system funded by a tax would not raise constitutional questions.

“I’ve said from Day One that if Medicare is constitutional, Medicare for everyone is constitutional,” said Randy E. Barnett, the Georgetown law professor who is representing one set of challengers to the health-care act.

Walter Dellinger, a strong supporter of the health-care act, said he finds it hard to believe that if a single-payer plan would be constitutional, “that the court would then stand in the way of a more market approach” of relying on private insurers to provide coverage.

He agrees that the court’s 1937 decision on Social Security does not provide a definitive answer, but he is looking to Cardozo’s words in the Helvering decision nonetheless in the amicus brief he is preparing for the Supreme Court.

“Whether wisdom or unwisdom resides in the scheme of benefits set forth . . . it is not for us to say,” Cardozo wrote. “The answer to such inquiries must come from Congress, not the courts.”