During Salvador vacation week, rightists play for power

''Everyone has gone to the beach.''

This is how one Western diplomat in San Salvador described the prevailing mood here as the traditional semana santa (Easter week) holiday took hold and perceptibly slowed the frenetic pace of the politicians.

Jose Napoleon Duarte, for example, the Christian Democratic President of the civilian-military junta, is in Costa Rica this week.

He left behind him his own aides to haggle out a compromise that would still give his ruling Christian Democrats a foothold in the new but as-yet-unformed government.

After a week of intense political maneuvering in the wake of the March 28 elections - in which no single party won a majority - the prospects for the Christian Democrats don't look good.

At least this is the impression gained from an April 5 meeting that brought together all six parties involved in the March 28 elections. Apparently the two major rightist parties agreed that the centrist Christian Democrats should be excluded from ''key positions'' in the new government. These parties favor one man, rather than a junta, leading the new government, and that would effectively diminish the influence of the Christian Democrats.

The slower pace here in the capital is in sharp contrast to a resurgence of guerrilla activity in the countryside. The terrorists, who were rebuffed at the polls when well over a million Salvadorans voted for peace, have sprung back into action after apparently lying low for a few days.

In a major assault over the weekend, some 800 terrorists equipped with bazookas and mortars attacked and seized a military base near the Chinchontepec volcano in San Vicente Province.

Despite this fresh wave of terrorism, politicians remain preoccupied with who will govern this tiny Central American nation.

Political observers say informal talks will continue throughout the week in the Salvadoran capital in an effort to break the political deadlock preventing the formation of the new government.

Although five right-wing parties have enough assembly seats among them to obtain a majority in a coalition government, they still are short of the two-thirds majority needed to govern with authority. This is the crux of the current Salvadoran dilemma and the reason for the political maneuvering since the election.

According to political analysts here, two formulas are being bandied about in the negotiations for a coalition government to take the country toward presidential elections. (When the constituent assembly convenes later this month , it is expected to schedule elections for 1984.)

The United States and Venezuela have worked exhaustively to end the Salvadoran political impasse, and they are pushing a formula that calls for a government of ''national reconciliation.'' It would include the Christian Democrats and the right-wing parties. The proposal allows for a three-man provisional government consisting of a Christian Democratic president, a member from one of the right-wing parties, and an Army officer. The president of the constituent assembly would be a member of a rightist party, and the vice-president, a Christian Democrat.

But the April 5 meeting in which the leading rightists indicated their intention to exclude Christian Democrats from top positions in a coalition government appeared to dim the prospects for adoption of this plan.

The other formula arouses strong opposition from President Duarte, the US, and the Venezuelans because it would exclude the Christian Democrats from any role in government. This coalition would operate on the assumption that no matter how much it might go back on land reform and human rights, the US would not cut off aid - military or otherwise - and leave El Salvador to the communists.

Both plans have their pitfalls. Neither Duarte nor Roberto d'Aubuisson, leader of the rightist Nationalist Republican Alliance, appears to be willing to make an accommodation. Mr. d'Aubuisson, however, who had been adamant that the Christian Democrats should have no part in the new government, has relented somewhat. He now says he is willing to include the Christian Democrats so long as Mr. Duarte stays out.

And differences among the right-wing parties themselves could make a right-wing coalition cumbersome as well.

The following profile of the political parties points up the differences among these rightist parties and between them and the Christian Democrats. It also helps explain the present impasse:

* Mr. Duarte's centrist Christian Democratic Party won 40 percent of the popular vote in the March 28 elections but garnered only 24 seats in the 60-seat constituent assembly, seven short of the number needed for a majority government.

The Christian Democrats, ruling with the military, began a program of redistributing the nation's wealth by expropriating landholdings larger than 500 hectares (some 1,200 acres) and organizing them into peasant cooperatives, and nationalizing banks and production of coffee and sugar.

* The right-wing Nationalist Republican Alliance (ARENA) led by Mr. d'Aubuisson finished second in the elections, seating 19 deputies in the assembly. (One of the ARENA deputies elected last week, David Joaquin Quinteros Melendez, was killed mysteriously April 3.)

Mr. d'Aubuisson is supported by wealthy landowners and businessmen, and has been linked in the past to ultra-rightist death squads and to the assassination of Archbishop Oscar Arnulfo Romero in March 1980.

* The National Conciliation Party (PCN), the offical government party until a 1979 coup, came in third in the voting with 14 assembly seats. The PCN opposes the Christian Democratic plan for cooperatives, which it - and the other rightist parties - sees as one step closer to communism. They call the Christian Democratic plan ''communitarism.'' But the PCN has said it will not end the Duarte-initiated land-redistribution policies.

* The more moderate right-wing Democratic Action Party won two seats in the assembly. Rene Fortin Magana, the party's leader, says he will accept the Christian Democrats in a coalition government - but without Mr. Duarte.

* The Conservative Salvadoran Popular Party took the remaining seat with 3 percent of the vote, and the Popular Orientation Party went without a seat.

In some countries political deadlocks involving coalitions are resolved in new elections. In El Salvador, such an impasse may be settled with guns. And with leftist guerrillas waiting to take advantage of such a situation, the Army may decide to settle the dispute itself if the politicians do not.