Some saw it as a monumental intrusion of the federal government into the life of the nation. Others predicted that its generous benefits would bankrupt the federal budget.

But today, 50 years after President Franklin D. Roosevelt signed one of the most revolutionary laws in history, the Social Security system has survived every political and economic threat to its existence.

The Social Security Act of 1935 was, as Health and Human Services Secretary Margaret M. Heckler puts it, "the most significant piece of domestic legislation" in the 20th century, one that "has done more to lift and keep Americans out of poverty than any other government initiative."

It was spawned in the depths of the worst depression the country had ever known. Unemployment had soared to 20 percent for the workforce as a whole, and to 30 percent for nonfarm workers. By the end of 1934, an estimated 19 million Americans were surviving on emergency relief.

For the 7.5 million citizens who were elderly, the situation was particularly bleak. At least half relied on others for their support because pensions and welfare programs were virtually nonexistent.

Only about 180,000 elderly people received old-age assistance from their states, with the average monthly benefit amounting to $19.74. And only about 150,000 retirees received pensions from private employers.

There were no official poverty statistics at the time, but as late as 1959, after a decade of postwar economic progress but before the Social Security system had had a chance to "mature," 35 percent of the elderly lived below the poverty line, compared to 22.4 percent of the population as a whole.

Today, only about 14 percent of the elderly live below the poverty line, about the same proportion as the general population.

The Social Security system's myriad programs -- for the aged, disabled, the unemployed and poor children who lack the support of a father -- distributed $175 billion worth of benefits in fiscal 1984 to roughly 36 million Americans -- one out of every seven.

Social Security retirement benefits now represent about 40 percent of the income of Americans over 65, by far the largest source. And three-fifths of all elderly households in this country relied on Social Security for at least half of their income in 1982.

While the Social Security legislation marked a radical departure in American life, it was billed by its supporters as conservative in many respects. The chance to create a broad new security system, Roosevelt said at the time, "is too precious to be jeopardized now by extravagant action."

While the retirement system he envisioned would be administered by the federal government, the states would decide the benefit levels and rules for the other income-support programs. Still, the plan stopped short of the social security systems of many European countries, providing no national health insurance, disability insurance, maternity benefits or temporary disability benefits.

According to former Health, Education and Welfare secretary Wilbur J. Cohen, who helped craft the plan early in his Washington career, Roosevelt wanted to ensure that the system would be insulated from political attack and thus survive beyond the Depression. As a result, the system's architects decided to create a plan under which everyone who had worked would receive retirement benefits, regardless of their income, rather than a system in which only the neediest would qualify.

Welfare systems, the planners reasoned, serve only a small and politically weak segment of the population. They also believed that welfare payments did not amount to real security because a person had to be poor before he could qualify.

Instead they decided that an automatic pension, financed by a person's own contributions over a lifetime and paid regardless of income and assets, would be a much sounder foundation for retirement.

The system they envisioned would be supported by a payroll tax, half paid by employers and half by their employes. Initially, each was to pay 1 percent of the first $3,000 of an employe's annual earnings; today the rate is 7.05 percent on the first $39,600.

In addition to retirement benefits, the package they prepared included federal matching grants to the states for welfare to the aged, the blind and dependent children, a requirement that states set up unemployment insurance programs, and grants to state and local governments for a variety of health services for women and children.

On Jan. 17, 1935, Roosevelt sent Congress his proposal.

Conservatives saw the new system as a giant tool for increased federal control. They feared that the Social Security trust fund would become a slush fund to finance Roosevelt's favorite New Deal projects, free from congressional control.

Many businesses disliked the prospect of a new payroll tax. And on a purely partisan level, many Republicans saw the system as a Roosevelt scheme to buy votes in the 1936 election with promises of lavish future benefits that ultimately would bankrupt the Treasury.

In the House, supporters of Dr. Francis Townsend, the apostle for the elderly, campaigned for his plan to pay $200 a month to every American over 60 at a time when the average wage in the United States was only $75 a month. Townsend proposed to finance the payments through a sales tax; opponents said it would break the bank.

The Roosevelt proposal instead included matching grants to the states to provide benefits of up to $30 a month to the elderly poor. The Townsend proposal was defeated, 206 to 56.

Also defeated was a plan that would have helped cover the costs of disabilities, childbirth, illnesses and industrial accidents. It would have been financed by taxes, mostly on upper-income people.

A Republican motion to increase charity payments to the aged but strip out the new retirement benefits was rejected, 249 to 153, despite the support of 95 of the 96 House Republicans who voted. Members of both parties then supported final passage of the bill, 372 to 33.

Because the old-age benefits were not scheduled to begin until 1942, many Republicans figured they would have another chance to kill them, and, in the meantime, would support the legislation's welfare provisions. (As it turned out, the first monthly retirement check -- totalling $22.54 -- was sent out on Jan. 31, 1940, to one Ida Mae Fuller.)

In the Senate, Huey P. Long (D-La.) introduced a "share the wealth" amendment to provide generous pension and unemployment benefits financed by a tax on assets, rising from zero percent on the first million dollars of an individual's wealth to 99 percent of his wealth over $8 million. The provision was defeated.

Again, a majority of Republicans voted to delete the retirement benefits. But again, that amendment was rejected and the legislation passed, 77 to 6. When Roosevelt signed the bill on Aug. 14, it marked a legislative revolution that had taken just under seven months.

"We can never insure 100 percent of the population against 100 percent of the hazards and vicissitudes of life," Roosevelt said that day, "but we have tried to frame a law which will give some measure of protection to the average citizen and to his family against the loss of a job and against poverty-ridden old age."

Still, as the 1936 campaign approached, Republican National Chairman John D.M. Hamilton warned that the Social Security system eventually would lead to a requirement that every American wear a dog tag.

But with time, Republican resistance faded. Presidents Dwight D. Eisenhower and Richard M. Nixon supported expanding the system, and Nixon, in fact, backed the idea of making cost-of-living adjustments automatic on an annual basis. This year, some congressional budget-cutters have looked longingly at the billions of dollars they could save by delaying the next increase in benefits, but so far Social Security has proved untouchable.

With adjustments that Congress approved in 1983, the Social Security system now looks as if it will remain financially sound well into the next century. Still, some observers are concerned about how the system will cope with the flood of baby-boom retirees who will be drawing benefits after the first quarter of that century.

"The act does not offer anyone, either individually or collectively, an easy life -- nor was it ever intended so to do . . . . ," Roosevelt said three years after the legislation was passed. But the benefits "will furnish that minimum necessary to keep a foothold; and that is the kind of protection Americans want."

Based on information supplied by the government, part of the answer to the Aug. 22 Federal Report quiz was incorrect. The Social Security Act of 1935 did not specify a date by which states had to start paying unemployment insurance benefits. However, under the law it was expected that most states would begin paying benefits in 1938, and in fact, 30 jurisdictions, including the District of Columbia, did. The rest began paying them the next year. Wisconsin was the only state that paid benefits before 1938, under a state law that was passed before the Social Security Act.