Philippine opposition faces a rocky road in uniting its ranks. It has yet to choose challenger to Marcos

Opposition leaders here face a tortuous battle in uniting their ranks. Leaders of the nation's two largest opposition groups decided last week 4/18 to field a common candidate in the 1987 presidential elections. But they have not picked a candidate, nor have they agreed on how to select one. Also they need to come up with a common platform.

The opposition has tried several times to become more unified since the assassination of opposition leader Benigno Aquino Jr. in 1983. None of these attempts has been successful.

Last year, amid reports that President Ferdinand Marcos was ill, an opposition group devised a process for choosing a candidate, should the President die and emergency elections be called. Led by Corazon Aquino (the widow of Benigno Aquino), former Sen. Lorenzo Tanada, and businessman Jaime Ongpin, the ``Convenors'' group suggested that the candidate be chosen by a small number of opposition leaders.

However, political parties under the National Unification Committee led by Salvador Laurel believe in holding a national convention to select a presidential candidate.

Between them, these two groups represent more than a dozen national and regional opposition parties. Though they now plan to work together, many here remain unsure, and even skeptical, that the Philippine opposition can rally behind one leader. Division is perceived to run deep, and the opposition forces have two very different ways of working.

Some oppositionists, such as the Convenors, prefer to fight the Marcos regime from the ``parliament of the streets'' -- through such activities as massive demonstrations and workers' strikes. Leaders of such groups called for a boycott of the 1984 National Assembly (parliament) elections but have pledged to participate in the future.

More ``traditional'' politicians, among them members of the National Unification Committee, on the other hand, are out to unseat the ruling party in elections -- the only way they believe reforms can be practically achieved.

Both types of groups now agree that it is ``best and logical'' to come up with a single candidate because chances of winning will be much greater. The opposition enjoys popular support, since many Filipinos are disaffected with the Marcos government.

Yet there remains some question that the opposition will rally behind one leader. Some opposition leaders admit they would support another candidate if the one who is chosen is perceived as not being for genuine reform.

``We cannot go for a bad deal,'' said Leandero Alejandro, an official with the Coalition of Organizations for the Realization of Democracy.

Some observers say the opposition will probably emerge victorious in local elections in 1986, barring massive fraud and violence. If so, this would pave the way for victory in the presidential elections, they say.

In last year's parliamentary elections, 55 percent of the total vote went to the opposition. Luis Villafuerte, an opposition member of parliament, said this happened despite the ``enormous amount of money'' the majority party had and their ``far superior [political] machinery.''

The ruling KBL party (Movement for a New Society) is also flexing its muscles, vigorously getting ready for elections. President Marcos has made it clear that he will run in the 1987 elections.

Marcos said Sunday that he is sure to beat any opposition candidate by a ``decisive majority of 2 to 1.'' He based his optimism on the results of ``the most recent survey.''

Amid preparation for the elections, a new opposition group has been formed. It is one many are watching. The group, named Bayan (a Filipino acronym for New Nationalist Alliance), is headed by former Senator Tanada, Jose Diokno, and Agapito Aquino, brother of the slain Benigno Aquino Jr.

Bayan is seen to be a novelty in Philippine politics because it promises to engage in both protest actions and elections as ways to fight the government. Aquino says the new federation seeks to blend the two processes which before had been viewed as contradictory.

Bayan intends to form its own political party. Mr. Diokno said in an interview that Bayan needs to consolidate itself so that it can negotiate with political parties ``from a position of strength.''