It began in 1974 as the ultimate liberal job creation bill: Commit the federal government to reducing the overall unemployment rate to 3 per cent, mandate massive new job programs to get there, institute national economic planning, and guarantee a job for everyone who wants one. By 1976, supporters dreamed it would prove the catalyst to revive the old Roosevelt coalition. Hopes ran high that it would become a keynote of the campaign.

Last week, ten months after a Democrat recaptured the White House, supporters of the Humphrey-Hawkins bill, as the measure is known formally, got their first big victory - the backing on the President.

But the legislation may provide more problems than action. Now a shadow of its earlier self, the bill already is being scoffed at by the White House, and conservatives are deriding it as inconsequential. The question is, was it worth the effort after all?

To be sure, the new legislation isn't all fluff. On a theoretical level, it provides the first serious sequel - and a significant step forward - from the last major goal-setting law, the 1946 Employment Act. That measure effectively sanctified Keynesian economic dogma (that the government could - and should - manage the economy) and established the Council of Economic Advisers. It was the first formal recognition that government has a role in economics.

The Humphrey-Hawkins bill would take this a step further by setting a firm numerical economic Advisers. It was the first formal recognition that government has a role in economics.

The Humphrey-Hawkins bill would take this a step further by setting a firm numerical economic goal - in the latest version, an overall unemployment rate of 4 per cent - and committing the goverment, morally, to trying to achieve it. And significantly, it would legitmize the use of structural measures to fight unemployment - the kind of "targeted" programs such as job corps for teenagers - the way the 1946 bill sanctioned the use of broader policies.

Importantly, too, the bill would, for the first time, tie the Federal Reserve Board, at least publicly, to the same goals the administration and Congress set.

Liberals were upset in 1976 when Fed chairman Arthur F. Burns rejected the notion thaa the Fed must adhere to the economic targets implied in congressional budget resolutions. The new bill establishes formal congressional goals and requires the Fed to take notice.

But beyond these lofty principles, the legislation endorsed by the President would do virtually nothing.

The measure would require the White House to "justify" its annual January budget and tax plans in terms of thwe per cent target. But analysts say that would be primarily a semantic problem, mainly affecting the President's speech writers. And Carter could propose changing the target after three years if he found it untenable.

Admittedly, the latest version of the bill is a decided improvement from the 1976 legislation, if only because it's less demanding on the economy.

The earlier prototype was almost universally criticized - First, for setting unrealistic goals, and then for boxing the government in which a mzssive new bureaucracy and new programs. Estimates then were that it would cost $28 billion a year to put Humphrey-Hawkins into effect.

The new bill has no price tag because it doesn't really mandate any new programs. But the goal still is considered unrealistic, if only because of the high proportion of teenagers and women now in the labor force. Both these groups have chronically high unemployment.

Economists say that to have to accommodate them in achieving "full employment" means having to spur the economy so fast it would exacerbate inflation.

Labor Department analysts who lined up to support the bill last week conceded it would take two $20 billion tax cuts and $9 billion in added public service jobs to reach the 4 per cent goal by 1983, as the bill urges.

But many economists doubt the target can be achieved even then. And the liberals' prescription doesn't account for unforeseen events, such as the 1976 oil embargo, which helped bring on a recession.

Moreover, the department's analysis would require little the administration isn't alreadly doing - or planning. The added public service jobs are included in the President's welfare reform package, and officials have been talking for weeks about periodic $20 billion-or-so tax cuts to offset the impact of inflation on tax brackets.

The question is, would these steps guarantee a 4 per cent jobless rate? most economists say no.

Indeed, the main impact of the measure appears to be as a political document. As critiss of the bill point out, the 4 per cent jobless goal will provide a convenient straw man that both sides will be able to use as a target - conservatives to decry as untenable, and liberals to cite as evidence that the administration is too cautious. (Even some of the measure's major backers are beginning to grumble about the compromise.)

The new version is the result of months of negotiations between the White House and key sponsors of the legislation, dating from last summer, when the President first began considering seriously endorsing the bill.

Carter opposed the 1976 version from the start on the advice of his lieutenants, but pledged to support it in principle after a camaign slip (his allusion to "ethnic purity") required a concession to black leaders.

The pledge remained only a gesture for months after Carter took office, with the President begging all questions by insisting he wasn't familiar with the latest version of the bill.

Late in July, however, the 32 liberal groups rallying to support the legislation - blacks, labor and a variety of social action organizations - petitioned hin for action. Early in August, the negotiations began.

What held up the talks for much of the fall - until even the critics were asking what the problem was - was a split between both sides over the bill's basic economic goal.

The sponsors wanted to retain the 4 per cent target for the short-range and then set an even lower goal for two years later. The White House sought to boost the initial figure to 4.75 per cent by 1981 (its publicly-stated target anyway) and leave the later years open.

There also was the issue of inflation. Sponsors wanted nothing that would give the administration a chance to shelve, the unemployment targets if inflation should begin to accelerate, which was exactly what the White House contended was necessary. And there was a good deal of arguging over whether language proclaiming that everyone had a "right to a job" really meant that, or merely was symbolic.

It was early November before the two sides finally hammered out a compromise: The jobless target would remain 4 per cent, but would be stretched over five years instead of four; there would be language giving the anti-inflation flight equal billing with the war on joblessness (while vowing not to scrap the battle against unemployment if prices soar). And - importantly - Carter could propose revising the goals after the 1980 election.

The changes, along with the shelving of the "right to a job" clause, were major concessions, but the Humphrey-Hawkins sponsors were in no position to argue. "We knew we knew we needed the President's support," one insider conceded, " o get the measure passed."

The bill was drafted jointly by Sen. Hubert H. Humphrey (D-Minn.) and Rep. Augustus F. Hawkins (D-Calif.). Humphrey, stricken with cancer, kept in touch by telephone from his bed in Minnesota.

By the time the compromise was unveiled, neither side was particularly ecstatic over the final version. At a background briefing last week, top administration officials predicted the bill would make little difference in formulation of White House economic policy. And sponsors of the legislation were beginning to hear protests from the more activist groups in the coalition backing the jobs effort.

In all, the thrust of the new bill seems largely symbolic - a sort of spiritual commitment to liberals that the administration will "care."

The difficulty is, the symbolism cuts two ways: While the bill is a victory for blacks and organized labor, it's also an anathema to business, which regards it as inflationary. As a result, Carter may be getting more than he bargained for politically.

With the new presidential endorsement in hand, prospects for passage of the bill now seem improved substantially. Congress, which refused even to consider the legislation in previous years, is expected to pass the watered-down version in 1978 - in part as a "monument" to Humphrey.

No doubt Carter will sign it with some flourish as evidence of his commitment to blacks and the Democratic platform (the platform contained many of the bill's key elements, though not formally tagged as such).

But to many observers, the question is, what will the measure really accomplish? To the extent that it commits the government to begin structural job programs that deal specifically with the hard-to-employ, perhaps the legislation will be considered a success.

But many economists fear it also will raise expectations beyond what this administration - or any other - reasonably can deliver. If that happens, Carter may wish in 1980 he'd listened harder to his advisers in the 1976 campaign.