Washington — Recent and impending developments in both El Salvador and Washington are combining to spell rough going for President Reagan's $8 billion aid program for Central America. In El Salvador, battlefield setbacks for the US-supported Army and uncertainty over next month's Salvadorean elections, make some senators and representatives reluctant to vote for substantially increased military aid.
In Washington, a key House subcommittee chairman, Rep. Clarence D. Long (D) of Maryland, said confidential studies completed in recent months by a private consulting firm and by the General Accounting Office showed that controls over the Salvadorean foreign-exchange system and over US aid expenditures in El Salvador were virtually nonexistent.
''I can hardly see liberals voting for $8 billion to Central America when Ronald Reagan says we've got to cut all kinds of domestic spending,'' Representative Long said in a telephone interview. ''How can you tell people you voted against education and then vote a lot more money for Central America?''
Meanwhile, last week's resignation of President Reagan's special envoy to Central America, Richard B. Stone, appeared to confirm the impression some congressional liberals had that the administration is making no progress toward a negotiated settlement in the region. Some liberals are convinced that the administration has no interest in such a settlement.
State Department officials argue, however, that the administration's rapid replacement of Mr. Stone by a career diplomat, Harry W. Shlaudeman, shows that Reagan considers the special envoy's role to be important. Officials insist that Stone's resignation did not reflect any change in policy but resulted from conflicts with Langhorne A. Motley, the assistant secretary of state for inter-American affairs. According to one report, Stone felt that he was not being fully informed by Secretary Motley of State Department thinking on a number of matters.
The choice of Mr. Shlaudeman to replace Stone is considered controversial by some congressmen because of congressional testimony Shlaudeman gave in 1974 concerning the overthrow of Salvador Allende, the Chilean leader killed in a military coup in 1973. Shlaudeman denied the United States had played a role in Allende's fall. It was later revealed that the CIA had made secret payments to Chilean opposition forces.
Long said that given Shlaudeman's service in Argentina, he was ''not a type who is going to inspire a great deal of confidence.''
President Reagan sent legislation to the Congress last Friday that embraced the essentials of the Kissinger commission report on Central America, which was given to the President last month. The legislation includes proposals for significantly increased levels of military aid to the region, as recommended by the bipartisan commission. But the President did not accept the commission's recommendation that military aid to El Salvador be contingent on demonstrated progress toward political and judicial reforms and termination of the activities of the so-called death aquads there. Earlier, Mr. Reagan had vetoed such legislation.
The House subcommittee on Western hemisphere affairs, chaired by Rep. Michael D. Barnes (D) of Maryland, is to hold hearing on the aid package this week. Representative Barnes has repeatedly raised questions about the administration's handling of human rights issues and about the efficiency of the aid program in El Salvador. Last month, Barnes reported that a confidential study commissioned by the Agency for International Development had shown abuses in the use of aid funds by the Central Bank of El Salvador.
The administration is counting on Dante B. Fascell (D) of Florida, the new chairman of the House Foreign Affairs Committee, to help form a bipartisan consensus on aid to Central America. While voicing criticism, Representative Fascell has often voted in basic support of Reagan's Central America policies. But taking into account large US budget deficits and sharp domestic spending cuts, the congressman questions the size of the five-year, $8 billion aid package. The Senate will take up the aid package in March.