Washington — The shifting winds over US policies in Central America are changing directions again on Capitol Hill. Only a few weeks ago, both houses and some leaders in both parties were lambasting the President over the US role in mining harbors of the leftist country of Nicaragua.
But since then, events have strengthened the President's position. Not only did the lawmakers return home for a recess and cooling-off period, but El Salvador has apparently elected reform candidate Jose Napoleon Duarte, long known and widely respected in the US Congress, as its president.
President Reagan is capitalizing on his opportunity by delivering a television address tonight on Central America, just as the House takes up a $10. 5 billion foreign aid bill that includes money for the region. If the speech accomplishes nothing more, it has already forced House Democrats to delay voting on the controversial portions of the bill until the President has spoken.
''It's always been obvious to me that the whole Central America issue needed to be more clearly defined to the American people,'' says House minority leader Robert H. Michel Jr. The Republican adds that in talks with his Illinois constituents he can ''sense that people don't understand.''
But even without a persuasive Reagan speech, Congress is already poised to vote some assistance for El Salvador, where the government is under siege from leftist guerrillas. The expected election of Mr. Duarte, who may soon visit Washington, all but assures the aid, it is felt here.
''I think it's going to be a plus for the administration on the Hill,'' says Rep. Jim Leach (R) of Iowa, a member of the House Foreign Affairs Committee who opposes US military involvement in Central America. ''Duarte has met with the Congress on more substantive issues than the President,'' says Representative Leach, who calls the Salvadorean leader highly respected among American lawmakers and a ''very credible individual.''
House majority leader Jim Wright (D) of Texas, reacting to the Salvadorean election and its effect on aid money, told reporters, ''I suppose it would help.''
Some in Congress say a majority has always backed US aid for El Salvador, especially in an election year when lawmakers might be held accountable for losing the country to communists. ''There's a strong feeling that they'd be fearful with regards to El Salvador,'' says House Speaker Thomas P. O'Neill Jr., who opposes any military aid for El Salvador. The Massachusetts Democrat has often conceded that he held a minority view on that issue.
Among those on the other side are minority leader Wright, who early this week criticized the Democratic version of the foreign aid bill for putting too many restrictions on the aid.
The votes on Central America aid this week will be largely symbolic since they come on the 1985 foreign assistance bill, which authorizes but does not actually spend money. However, it will probably accurately reveal House members' mood.
They can choose a House Foreign Affairs committee plan that would cost about , and place human rights requirements on El Salvador. The committee version would also severely cut back from 1,700 to 300 the number of US military personnel in nearby Honduras.
But the GOP will be pushing for another plan, granting all of the Central American money Reagan requests (about $1.5 billion in military and economic aid) while lifting limits on the number of US advisers in El Salvador (now 55), and of military personnel in Honduras.
The two plans, which will probably come up for a vote on Thursday, are given an equal chance by some House sources. A third, even more stringent version proposed by Rep. Gerry E. Studds (D) of Massachusetts, would limit aid more stringently but is not seen as likely to pass.
A GOP victory in the aftermath of the Reagan speech may only be symbolic. But it will point to winning a vote when the House goes back to work on an urgent supplemental bill that includes a proposed $62 million for the El Salvador military. It was stalled in the House during the controversy over US mining in Nicaragua.
''I think the El Salvador funding has broad-based support now because of the election'' of Duarte, said GOP assistant leader, Sen. Ted Stevens of Alaska.
The same is not true of money for covert action against Nicaragua, he said. ''It's pretty clear that Nicaragua (covert action money) will not survive,'' said Stevens who favors action against that government but who called the recent US aided mining ''the colossal blunder of all covert programs.''