CONGRESS AND CONTRAS. Democrats seek right political strategy for blocking contra aid. Congressional majority lacks policy of its own

Slowly, unenthusiastically, congressional battle lines are being drawn on aid to the Nicaraguan contras. The issue is whether the United States should send the contras the final $40 million of the $100 million in military and nonmilitary aid already approved by Congress.

As usual, the majority Democrats are generally opposed to additional aid to the rebels who are trying to mount a credible offensive against Nicaraqua's Sandinista government. Republicans appear at least to favor not blocking release of the remaining $40 million of the amount already approved by Congress.

Democratic lawmakers, sensitive to charges that they oppose the Reagan administration's Central American policy without supporting a viable alternative, are groping to come up with a strategy for the region that can stand in contrast to present US policy. Republicans are looking for a way to head off an embarrassing congressional rebuff to the White House's Nicaraguan policy.

Members of both parties who voted for contra aid last fall are loath to reverse themselves on the subject now.

And some believe the appointment of Howard Baker Jr. as White House chief of staff has changed the political equation, ultimately preventing the defection of some contra-aid supporters.

``Some people would just as soon forget about this,'' says Rep. Sam Gejdenson (D) of Connecticut.

But there will be no way for lawmakers to avoid the matter once the administration formally notifies Congress that it wants to release the second and final installment of the aid package, as it is expected to do within the next two weeks. The $40 million will be on its way unless both houses of Congress vote within 15 days to halt the funds.

The President is certain to veto any legislation blocking the funds, and even the contras severest congressional critics concede that it would be impossible to muster the necessary two-thirds support in both houses to override a presidential veto.

So the debate has focused on the tactics and strategy of what is certain to be a symbolic vote - one that will set the stage for a debate later this year over President Reagan's request for an additional $105 million in contra aid.

Nose counts among Democrats in the House indicated that lawmakers did not like voting to halt the very same funds they had approved only months before.

Now the majority party seems set to unveil an approach that would link the release of any further funds to a full accounting of all contra aid by the Reagan administration. In proposing a moratorium, instead of an absolute halt on the aid, Democratic leaders expect to attract more votes than they otherwise would have.

The Democratic package stands in contrast to a Republican proposal, unveiled last week, which would postpone consideration of the $105 million package for six months to see if Central American peace talks now under the direction of Coast Rican President Oscar Arias S`anchez produce any results.

``The Republicans are just playing with mirrors,'' says House deputy whip David Bonior (D) of Michigan, a member of the House Democratic task force charged with fashioning a strategy on the contra aid vote. ``If they were serious, they would talk about delaying the $40 million.''

Nevertheless, the Democrats' moratorium plan might run into trouble in the Senate, where members are allowed great leeway to gum-up legislation. It would likely be the object of filibusters and other obstructionist attempts to derail its passage. Even without such efforts, the moratorium's passage is not guaranteed.

Whether the House passes a moratorium or a resolution of dissaproval, the Senate vote will be very close. Senate Democratic whip Alan Cranston (D) of California says he counts 50 votes in favor of the disapproval resolution in the 100-member body.

A number of Democratic sources say they believe that Mr. Baker could be key in persuading wavering members not to vote against the contras at this time, thus sending the symbolic effort to defeat.

That leaves more than one member wondering why Democratic leaders do not just forget about a vote on the $40 million and focus their efforts, instead, on defeating the $105 million request later this year.

``I think we could be playing with fire,'' one Democrat says.

But doubters seem to be in the minority. Democrats sense that many contra supporters in Congress are looking for a change, and that now is the time to begin a year-long attack on Reagan's program.

``We have to begin searching for an alternative,'' says Rep. James Slattery (D) of Kansas, who is circulating a cease-fire plan that has begun to attract the support of conservatives and liberals, including contra-aid supporters. ``It's important that the President know that the old support just isn't there anymore.''