While the deficit for the current fiscal year may end up $10 billion below the original estimate of $68.8 billion, the projected deficit for fiscal 1978, which starts Oct. 1, has grown by more than $15 billion since it first was proposed by President Ford in January.

Furthermore, as the House and the Senate budget committees complete their work on the first leg of the congressional 1978 budget, pressures to spend more will not evaporate.

At a time when retail and wholesale prices are accelerating and Wall Street is getting visibly nervous about inflation, the two-year-old congressional budget process is trying to weigh both the need to stimulate the economy and get spending under control.

For President Carter, who has set a firm goal balancing the federal budget by 1981, the 1978 developments must appear threatening. The $57.7 billion deficit he proposed last February ($10.7 billion bigger than Ford's), will grow, Office of Management and Budget officials concede, although they do not think his programs would result in a $66 billion deficit - a level calculated roughly be Senate Budget Committee experts.

By anybody's calculation, the 1978 budget appears as if it will be bigger than the revised 1977 estimate of $57.7 billion, even though the economy is supposed to be in better shape in 1978 than in 1977.

"We seem to have developed a habit of $60 billion budget deficits," Senate committee chairman Edmund S. Muskie (D Maine) complained last week as he exhorted his committee to go back over the numbers it had adopted tentatively and trim $2 billion. It did. That belt-tightening also saved Republican support for the measure.

Still, the Senate committee approved a budget with a deficit of $63.2 billion and its House counterpart earlier had approved a $64.3 billion deficit. Rep. Robert N. Giaimo (D Conn.), chairman of the House Budget Committee, concedes that when the committee's budget comes to the House floor for a vote after Easter recess, the committee will have to add about $1 billion more to its spending estimates - and therefore its deficit estimates - to account for higher payouts to crop support programs.

Both the House and the Senate budgets face potential pressure from the nemesis of underspending which has plagued federal budget watchers for the last two years. It is this so-called shortfall which casued President Carter to revise downward the $68.8 billion deficit projected for fiscal 1977.

The budget deficit also came in well under original estimates in fiscal 1976 because federal spending was not as big as congressional and administration officials thought it would be.Officials still are not sure whether they simply overestimated potential spending or whether they jsut were off on the timing and funds which they expected would be spent in 1976 or 1977 will get spent later.

House committee chairman Giaimo worries that, while the spending is not showing up in 1977 when it is needed to stimulate the economy, it will show up later when the economy is moving closer to full employment, "creating havoc in that year."

But it is not only the potential of the shortfall "bubbling up" in the future that concerns budget watchers. They think the committees still do not come to grips with longer-range issues.

The two-year-old congressional budget process is designed to give Congress the same tools the President has had in dealing with overall spending, in balancing spending in one area against spending in another, and using the spending and taxing powers of Congress as an economic tool.

Muskie argues that the process cannot truly come of age until it also looks carefully at the long-range spending impact of the current budget. The committees do discuss long-range issues more, but Muskie said in an interview not to "the degree I think is necessary." He said he has resisted the creation of subcommittees, because they become little "dukedoms" which lose concern for overall budget issues, but said he may have to create them to focus attention on long-range budget issues.

Among those issues are Social Security reforms, national health insurance and the return to the budget of a large number of federal agencies whose spending does not get counted now under the law.

Robert Boyd, minority staff director of the Senate Bedget Committee, said the committee appears to realize that current programs which have little spending impact in the year in which they are enacted can create big claims on federal resources several years in the future.

Giaimo has included in the House committee's report on the budget a series of recommendations on how to save money over the long run - including changing the way federal blue-colar pay scales are set, phasing out impact aid to education and selling off stockpiles. If followed, these recommendations would result in savings of $26 billion over the next five years, he contends.

But legislative recommendations from the budget committees have been overlooked by the House and Senate in the past. Sen. Ernest F. Hollings (D.S.C.), in proposing to spend $2 billion more on defense than the House, cited the both desirability of reforming blue-collar pay scales and the impossibility of getting such a change through Congress.

Congress must deal with both the long run and the short run in setting a federal spending agenda. The House and the Senate have taken only the first step along the road to devising a 1978 budget. The committee reports must go to the floor of their respective houses, then to conference, and must be approved by Congress by May 15. That budget becomes a guide to Congress in setting spending and taxing policy. By Sept. 15, Congress must pass a so-called second concurrent resolution which sets final, binding spending ceilings.

Both Muskie and Giaimo think their resolutions should survive floor fights relatively intact, although Giaimo says the committee's recommendation on defense spending - $2.3 billion belwo the President's request and $2 billion below the Senate level - will be attacked on both sides: from those who want to spend more on defense and from those who want to spend defense monies elsewhere, such as on housing.