President Carter is beginning his second year in office this weekend with a major strategy shift in his long-criticized economic game plan: He's pulling in his flashy end-runners and regrouping for a standard play.

In a blitz of press conferences and messages last week and in coming days, the President is outlining a series of new - and decidedly lower-key - economic and tax proposals designed to erase his image as an overpromiser and replace it with a picture of a more measured national leader who can carry out the job.

The only real question is whether it all will work.

The shift has come partly in response to adverse reaction to Carter's earlier, more ambitious proposals. Spurred by the momentum of a populist election campaign, the President last year bombarded the country with a spate of major new proposals ranging from an energy package and welfare "reform" plan to a bailout of the Social Security system and a promise of comprehensive tax revision.

As events since then have shown, however, the nation wasn't ready for all that at once. As a result, most of Carter's programs either have been scuttled or bogged down in Congress. And the administration has drawn criticism for lacking a coherent, well-defined economic program. The complaint most often heard was that the President "proposed too much."

But the change also reflects a belief by top Carter policy makers that, in the present economic circumstances, the job of managing the recovery must take precedence over other goals - or risk bringing on a recession that will delay any initiatives and only worsen existing problems. "Without adequate growth, we can't do anything else," one key aide mused last week.

This weekend, Carter is backing away from most of those earlier porposals and returning to a series of milder, more conventional programs designed to revive national confidence that he is tending to the economy.

The measures include:

A relatively austere budget policy that essentially limits spending to barely more than is needed to keep present programs apace with inflation. Although final figures are not scheduled to be made public until tomorrow, early estimates place total spending at just over $500 billion, with virtually no major new social initiatives.

A standard Democratic tax-cut package containing $24.5 billion inreductions for individuals and business designed to offset the "drag" created by the new Social Security tax increases and the impact of inflation in pushing taxpayers into higher brackets, and to add some stimulus to the economy. There's a series of modest "tax reform" proposals attached, but it's far short of the comprehensive revision Carter was planning before.

A modest anti-inflation program built maninly around continuing consultations between White House officials and key business and labor leaders in hopes of working out step-by-step solutions to specific problems that are driving up costs. Although top administration officials publicly are touting it as a major effort, most analysts say it's too squeamish to be effective.

Grudging support of a sharply diluted version of the Humphrey-Hawkins "full-employment" bill, which commits the government - symbolically - to reducing unemployment to 4 per cent by 1983. Although top administration policy makers still believe privately that the measure would be counterproductive, they're committed to endorsing it before Congress, and the bill now stands a good chance of passing.

If that sounds like the standard grab bag of traditional economic tools, that's exactly what it's supposed to be. In contrast to the frenetic days of the administration's first few months in office, this policy mix is designed to be dull - to make business and consumers more comfortable and, hopefully, to spur more confidence and better economic performance to boot.

Moreover, the downshifting will be accompanied by a more muted statement of Carter's economic goals, with a far more realistic appraisal of what actually is achieveable. Carter last week formally jettisoned his earlier inflation target - to slow the rise in prices to 4 per cent by 1981 - and hedged his unemployment goal from its previous 4.75 per cent by 1981 to a new 4.9 to 5 per cent. He also conceded there's only a long shot that he'll be able to balance the budget by that year.

There's no question the new proposals leave Carter less open to criticism as a pipe-dreamer. Although the President's new budget will produce another large deficit of about $60 billion, it essentially is a conservative plan. Geralf R. Ford wouldn't actually have proposed it, but he'd have been happy to get it back from Congress in place of more free-spending congressional proposals. The prospects are that liberals will complain loudly.

Besides a fairly hefty rise in defense spending, the rest is mostly internal rejuggling. Carter has included a stepped-up jobs program to soothe urban Democrats but, except for extending the present public service jobs plan, the rest is quite modest. And the highly touted urban financing plan to be proposed in March also is expected to be mostly show.

The tax package Carter is proposing already has been attacked by liberal economists as too small - providing barely enough to offset the present drag on the economy, with only a scant amount of new economic stimulus. And the "reform" portion contains only two moderately controversial changes - the phaseout of two foreign tax breaks Carter pledged earlier to cut back.

The anti-inflation package, no matter how high-sounding, is a long way from the tough wage-price restraint program President-elect Carter was touting 14 months ago - no numerical wage-price increases. Even the consultations with business and labor will be informal, not under any single umbrella group.

Finally, assuming he wins passage of the still-pending energy bill, Carter won't be pummeling the country with new programs as he did during the first year. Instead, say top aides, the emphasis will be on day-to-day management of the economy. The idea will be to create an image that will make business feel comfortable enough to spur investment.

What the Carter plan represents is an intentional gearing down of the administration's economic policy - in many ways, a shift from campaign rhetoric to reality. Carter tried careening along at the headier speed, but skidded - sometimes at his own doing - and never really succeeded. The failures were costly ones for him, politically. Now, he's slowing down.

The problem is, it may not do that much good, at least so far as the outlook is concerned. As administration policy makers concede privately, Carter still faces serious political and economic obstacles that, taken together, could leave him no better off than before.

There are these pitfalls:

Political squabbling over Carter's tax and budget policies is likely to result in tradeoffs that could give the President a far different tax cut and spending mix than he wants - and possibly dim even further his goal of a balanced budget.

While liberal economists are complaining that the $24.5 billion tax cut is too small, congressional leaders actually regard it as too large - and probably will balk at some of Carter's budget cuts as well. At the same time, many key Democrats want more emphasis on job programs.

The result could be a rejuggling by Congress to shift more dollars into spending at the expense of the tax cut - a change that would be easier for the law makers to swallow politically, but also would make it more difficult for Carter to balance the budget in coming years.

The President's anti-inflation program is unlikely to have very much effect - not only because it's too modest, but also because the inflation rate for the next few years largely has been set already - by the continuing built-in wage increases in the economy - and can't be altered dramatically.

The best most analysts are hoping for is to keep the price spiral from speeding up - and that the plan itself doesn't backfire and send business and labor stampeding for higher wage and price increases "in anticipation of" controls.

No matter what the President proposes domestically, his policies will be undermined by the new dollar crisis, which threatens to push interest rates higher, exacerbate inflation and jolt investor confidence. Carter must deal decisively with the dollar problem or risk political confrontation with U.S. allies and, possibly, a retaliatory oil-price increase.

Most important, the currency flap may inhibit Carter's new Federal Reserve Board chief, G. William Miller, from easing money and credit policies as the administration wanted. Top administration strategists were hoping for a change when conservative Republican Arthur F. Burns steps down as chairman. But Miller can't lower interest rates immediately so long as the dollar is ill.

There also is the danger of an "energy overhang" - a chance that Congress won't be able to break its present deadlock over the energy bill. If that happens, Carter may find he will have to act on his own to present a credible energy program needed to stem the decline of the dollar. But the breakdown could delay his tax and budget programs as well.

Finally, there's no guarantee Carter will be able to spur business confidence even with his shift to less "radical" policies. Indeed, although businessmen seem happy with the Carter tax-cut package, many already are complaining that the reductions for business are too small. And the business community is likely to be upset about the $60 billion budget deficit.

The latest survey of business capital spending plans shows that corporate investment in new plant and equipment - the key element needed to provide new thrust to the economy - will rise by only 4.5 per cent after adjustment for inflation this year, far below the 9 to 10 per cent rate the administration concedes is necessary for a robust recovery.

What it all boils down to is that, despite this deliberate gearing-down in policy, both Carter - and the economy - still face some trying times ahead. No matter what the President proposes, he still must satisfy diverse - and often vocal - constituencies whose goals frequently conflict. Some of these groups, it must seem, can't be satisfied at all.

Carter's own top policy advisers also are more muted. W. Michael Blumenthal, the Secretary of the Treasury, appears to most observers to sound decidedly more conservative than when he first took office. And liberal Charles L. Schultze, the President's chief economist, has bitten his tongue and shifted to the new go-for-growth approach.

It was Blumenthal and Schultze who - for different reasons - helped scuttle the earlier "tax reform" package. Blumenthal felt the sweeping overhaul of the tax system would be unsettling to business and investment. Schultze decided what the economy needed more than "tax reform" was a tax cut to offset the energy and Social Security tax increases. In both cases, pragmatism won out.

To be sure, there may be mixed emotions about the passing of the old Carter ambitions. On one hand, had the President succeeded in pushing through some of his earlier programs, he might be emboldened to try others - a prospect that wouldn't have been likely to warm the hearts of many more conservative Americans.

On the other, his failure cost him political momentum - and may have dashed prospects for liberal initiatives for many years to come. While officials talk vaguely of reviving the President's earlier tax-revision proposals in 1979 or 1980, most observers believe they won't show up again. The push that comes from a President's initial 365 days in office rarely can be duplicated.

Still, there's no doubt that policy is changing this month, and - some would say - changing for the better.