Washington — After an extended year-end break, the nation's lawmakers return to Capitol Hill today to deal with mounting foreign policy problems, escalating budget deficits, and the politics of an election.
The effects of electioneering will touch the Hill from the first week, when the House Democratic Caucus is slated to begin selecting 164 nominally ''uncommitted'' delegates to the Democratic national convention.
It will be the first time since 1824 that a congressional group has had a role in nominating a president, due to a change in party rules. Senate Democrats will also select delegates, but no date has been announced.
Aside from presidential poli-ticking, the top on virtually every list of concerns facing the returning Congress is Lebanon. From a circle of constituents gathered in the tiny farm village of Windsor, Ill., to the sophisticated communities of California, to prosperous builders on the outskirts of Chicago, the message to congressmen is the same: Bring the boys home soon.
''It's the No. 1 issue in this country,'' says a top aide to House Speaker Thomas P. O'Neill Jr. (D) of Massachusetts. The speaker has announced that he is about to change his position from supporting the agreement passed last year authorizing 1,600 marines to stay in the peacekeeping forces in Beirut for 18 months.
Unless there is evidence of progress, says the O'Neill aide, ''I think very early into the session the speaker will take whatever action is necessary.''
Although no specific legislation is proposed, it could take the form of a new law shortening the 18-month period. Other approaches include withholding funds and a congressional resolution calling for withdrawal. Senate majority leader Howard H. Baker Jr. of Tennessee said Sunday on NBC's ''Meet the Press'' that he felt he had enough Senate votes to block any move from the House to remove the US troops, ''barring unforeseen circumstances'' or a drastic change in the Lebanon situation.
Central America, the other major hot spot in the world, moves to the fore after several months on the legislative back burner. The $8 billion aid package just proposed by the Kissinger commission faces hearings and controversy on the Hill.
Aid to the embattled Central American nation of El Salvador will be a major stumbling block, with some on Capitol Hill (including O'Neill) willing to give economic but not military aid.
The White House can be expected to fashion a bill including both kinds of funding. And many members of Congress will be reluctant to vote for any foreign aid during an election year because such aid is rarely popular among voters. Senator Baker, however, predicts the Kissinger package will pass Congress virtually intact, including a certification process for El Salvador aid.
Although the second session of the 98th Congress will begin with foreign affairs, it will soon after confront the persistent red ink in the federal budget.
Democrats, who have already begun rapping Republicans for fiscal irresponsibility on the budget, have adopted the budget deficit issue as their own. They will have ample opportunity to exploit it when the President releases his annual budget, with expected deficits continuing in the $200 billion range.
But virtually no one on Capitol Hill now believes Congress will act this year to curb deficits. Sen. Bob Dole (R) of Kansas, chairman of the Senate Finance Committee, is still said to be working on a deficit-reduction package. But it will probably be little more than a symbol.
''This will be the year that American people are educated on the issues,'' says George A. Ramonas, an aide to Sen. Pete V. Domenici (R) of New Mexico, chairman of the Senate Budget Committee. ''And next year there'll be action.''
Meanwhile, for '84 the expected legislative theme is posturing and postponing. Posturing includes talk about the impending crisis in medicare and medicaid, as well as tax measures to cut deficits and, of course, debates over who created the deficit.
Congress has planned its shortest session since 1966, and it will have little time to pass major legislation on any subject. Most likely, it will complete only the required spending bills to keep the government agencies running and then hurry home to campaign for reelection.
Even immigration reform, to which Speaker O'Neill seemed to give a green light during the break, now is in jeopardy due to reports that White House budget director David A. Stockman opposes the bill as too costly. According to an aide, O'Neill will halt the politically risky bill unless the President reaffirms his support for it. Senator Baker Sunday said the administration was still backing the bill.
Other proposed legislation, from a new Clean Air Act to a tax bill, appear doomed, as Congress avoids controversy during the last months before the polls open.