First the rival camps of opposition candidate Corazon Aquino and President Ferdinand Marcos traded local politicians. Then they exchanged nephews. Now the focus has shifted to movie stars, and the Aquino campaign seems to be getting the worst of it.

Amid the charges, countercharges and general mud-slinging of the Philippines' presidential election campaign, the hardest blow appears to have been struck by the endorsement last week of Marcos by a 33-year-old actress, Nora Aunor.

The country's most popular performer, Aunor was a friend of the Aquino family and the goddaughter of the opposition candidate's sister-in-law and press aide, Lupita Kashiwahara. Aunor announced a week ago that she was joining the "Stars for Marcos" movement mobilized by the president's daughter, Imee Marcos-Manotoc, to stump for Marcos and his running mate, Arturo Tolentino.

The endorsement hurt the Aquino campaign, not least because the opposition had made much of Marcos-Manotoc's recent candid statement that "Cory" Aquino was "just like Nora Aunor" in her popular appeal. Evidently stung, opposition spokesmen reported that Aunor had been pressured into the endorsement because of tax and other problems with the government.

Regardless, the case illustrates the importance both sides are attaching to a battle for "defectors" and endorsements as the presidential campaign enters its final week. It is a battle that has split families and polarized political differences among otherwise close-knit groups.

Some of the defections and endorsements have been important not so much for the persons involved but for the family relationships they represent. Family and clan ties are often critical factors in bringing in votes for a candidate because of a tendency to follow the leader of an extended family on political questions.

Thus, both sides consider it a major coup when a relative -- the closer the better -- of the opponent breaks away from the family and comes out openly in support of the other side.

In this election, perhaps more than most, the families of the rival candidates have played key roles as advisers and campaign managers. The Marcos campaign essentially is being run by his wife and children, notably daughter Imee Marcos-Manotoc and son Ferdinand (Bongbong) Marcos Jr., while Aquino's is managed largely by an elder brother, Jose Cojuangco.

So far, there seems to be no clear overall winner in the battle, which began with the defections of several mayors and provincial governors from Marcos' ruling New Society Movement. In response, Marcos' party claims to have recruited opposition campaign personnel.

The main longstanding family split highlighted by the current campaign is that dividing the Cojuangcos, the family of opposition candidate Aquino. Her first cousin, Eduardo Cojuangco Jr., controls the country's coconut industry and is the leading multimillionaire friend of President Marcos. He also serves as the political warlord of his and the Aquinos' native Tarlac Province.

The matriarch of the Aquino clan, Dona Aurora Aquino, the mother of assassinated opposition leader Benigno Aquino Jr., calls Cojuangco a "financial Pac-Man" for his voracious appetite for wealth and power under the Marcos government.

Tarlac Province has been the scene of recent political violence in which a godson of Aquino was slain while campaigning for her.

Shortly after the killing, a nephew of Marcos' wife, Imelda, resigned from the Philippine foreign service and pledged support for Aquino. Norberto Romualdez III, 46, quit his post as commercial counselor of the Philippine Embassy in Brussels on Jan. 17, accusing Marcos of having ruined the economy and destroyed business confidence in the Philippines.

The Marcos camp retaliated a few days later with the announcement that Benigno (Bobby) G. Aquino III, 40, a nephew of the opposition presidential candidate, had "defected" to Marcos' ruling party. A government press release quoted him as saying he feared that his aunt would be manipulated by her advisers if elected and that this "could be disastrous."

Another prominent "defector" has been Leticia Ramos Shahani, a distant cousin of Marcos and sister of Lt. Gen. Fidel Ramos, the armed forces vice chief of staff. She endorsed Aquino early and was pressured to resign as an ambassador and a United Nations assistant secretary general on the ground that the Philippines foreign service forbids involvement in partisan politics. Opposition spokesmen have pointed out that the government seems to have forgotten this rule in the case of numerous diplomats working for Marcos' reelection, notably Ambassador to the United States Benjamin Romualdez, the brother-in-law of the president.

The Marcos camp's turn came with the endorsement of the president by Enrique Zobel, a wealthy businessman who had been considered sympathetic to the opposition. The endorsement last month shocked Manila's business community, which has lined up solidly behind Aquino, and angered some of her supporters.

On the other side of the political fence is a cousin, Jaime Zobel, and his wife, Bea. The Spanish-born Bea Zobel, who previously had been apolitical, announced her support for Aquino last week. "Those of us who have never been involved in politics before can no longer remain wishy-washy," she wrote in a newspaper commentary.

Other prominent families divided by the campaign have been the Moslem Dimaporos and the Dianalans, who wield great influence on the southern island of Mindanao. Brothers-in-law Ali Dimaporo, a longtime Marcos supporter, and Omar Dianalan, a defector to the opposition, have been pitted against each other.

The struggle among families has not stopped with the living but has even extended to persons long dead. Government-controlled news media lately have been recalling the World War II collaboration with the Japanese of Jose Laurel, the wartime president and father of opposition vice presidential candidate Salvador Laurel, and Benigno S. Aquino Sr., a member of Jose Laurel's Cabinet and father-in-law of Corazon Aquino.

A full-page newspaper advertisement for Marcos headlined "What Did Your Daddy Do When the Invaders Came?" charges that both the opposition candidates "are descended either by affinity or consanguinity, from the two leading figures of Filipino collaboration with the Japanese occupiers." The ad says that Marcos received five war wounds while his political counterparts were living comfortably. However, no mention is made of historical records that Marcos' own father, Mariano Marcos, was shot as a collaborator by anti-Japanese guerrillas, or of reports suggesting that Marcos falsified his war record as a guerrilla fighter.