Washington — Returning today for its final session of the year, the 98th Congress is settling into a ''bare necessities'' mode. Only legislation that must be passed is assured action, as Capitol Hill prepares for the 1984 elections.
The only exceptions will probably be proposals that find strong agreement in both parties, thus neutralizing the harm they might do during the campaign season.
''Congress is not in the mood to look for fights, and neither is the President,'' says Christopher J. Matthews, an aide to House Speaker Thomas P. O'Neill Jr. (D) of Massachusetts. ''There's a reciprocal desire to avoid fire fights.''
Moreover, the Democratic aide says, ''I don't think there's a drive to find extra things to do this year.''
''People become a little more cautious,'' says an aide to Senate majority leader Howard H. Baker Jr. (R) of Tennessee. ''It's probably much more difficult to launch out on new agenda items.''
Even old agenda items will have to wait, as Speaker O'Neill made plain earlier this month when he quashed hopes for immigration reform this year because of Hispanic opposition. His announcement had the sound of a trumpet call heralding the campaign season, disgruntling some, especially Republican leader Robert H. Michel of Illinois.
''It's gutless government,'' says a spokesman for Representative Michel. ''This is a nonelection year, and we're not doing anything. That's frustrating for Mr. Michel.''
Congress must complete appropriations bills to keep the government operating, as well as a few other required tasks, such as a Senate confirmation vote on William P. Clark, named as the new secretary of the interior. But most other action, including reducing the federal deficit, has been relegated to the nonessential list.
Both parties are proceeding gingerly on raising taxes. The House Ways and Means Committee tax bill, to be completed this week, is expected to include only 73 billion tax hike.
When the tax legislation arrives on the floor, the House leadership will probably give members a chance to vote for the whole $73 billion in new revenues. But the vote would be little more than a for-the-record display of concern over $200 billion federal deficits.
Such displays have already become part of a new Democratic campaign strategy which attempts to portray Republicans as spendthrifts, responsible for the biggest deficits in US history. Democrats are crowing over attention given $5, 000 worth of radio ads that reminded voters that candidate Ronald Reagan had promised to balance the budget by Sept. 30, 1983.
The Democratic campaign has ''poisoned the well'' of compromise and assured that there will be little deficit reduction this year, charges the spokesman for GOP leader Michel.
But a Democratic political strategist counters that even without the campaign , ''I don't think there are any hopes for compromise.''
Instead, both parties are now expecting a scaled-down budget ''reconciliation'' bill composed only of taxes and savings that have widespread agreement.
Even as it sticks to its must-do list, Congress is sure to see political sparks between now and adjournment Nov. 18. The resignation of Interior Secretary James G. Watt put aside one controversy and ushered in another. Capitol Hill is still recovering from the shock of the choice of Judge Clark, a close Reagan friend who has spent the last two and a half years in foreign affairs.
''If Judge Clark has any experience in or knowledge of natural resources or national parks, it has been a closely guarded secret,'' said Sen. Dale Bumpers (D) of Arkansas, who is expected to lead the opposition.
Congress will also be testing the steadying power of President Reagan's strengthened hand in foreign and security matters, now that the Soviet downing of the Korean airliner is off the front pages.
This week the House will take up the question of Reagan administration aid to armed insurgents fighting the Marxist government of Nicaragua.
A second test will be yet another MX missile vote, this one on a 1984 defense appropriations act. The House has already authorized the missile construction, but a switch of a handful of votes could withhold funding.
In other foreign-policy issues, the death of a fifth US marine by hostile fire in Lebanon last week points to the shaky conditions there. But the president has a bipartisan agreement with Congress over Lebanon in his pocket. Meanwhile, the so-called Kissinger commission is attempting to arrive at yet another bipartisan accommodation over Central America policy.
''Bipartisan'' is going to be a big word in the coming election campaign, predicted Democratic aide Matthews. Democrats in the House say they are making it work for them, too, since they expect to squeeze out of the Reagan administration at least $6 billion more for Labor and Health and Human Services programs than the president's budget proposed.