During 16 years in power, Philippines President Ferdinand Marcos has built a seemingly unbeatable political machine. He has relied heavily on the military during eight years of martial law, but he is also credited with what the Filipinos call political listo, or cleverness, in outwitting his opponents.

Now it seems the Marcos machine may have been a little bit too unbeatable. Faced with increasing polarization marked by steadily growing support for a communist insurgency in the provinces, Marcos is promoting a stronger moderate opposition.

But there is a feeling here it may be too late for that, and other problems may yet catch up with the Marcos rule. Besides the drift toward more radical opposition, a deteriorating economy and the absence of any clear successor to the 64-year-old strongman contribute to doubts about the future stability of America's most important ally in Southeast Asia. The question that crops up repeatedly is: Can a revolution happen here?

As with most matters of Philippine politics, there is no consensus on the question. But few would dispute that the New People's Army, the guerrilla wing of the Communist Party, is becoming a bigger factor and that the legal opposition has been divided, demoralized and weakened since Marcos scored a lopsided victory five months ago in a presidential election boycotted by most opposition groups.

In an interview at Malacanang Palace earlier this month, Marcos conceded that the New People's Army was "becoming more active," but he denied that this meant it was "gaining strength" or attracting adherents from the legal opposition.

The guerrillas "are gaining support in the form of funding, and we're trying to pin this down," Marcos said. "We suspect some of the funding is from outside."

He added, "I strongly suspect this is from people who are in the communist fringes in some countries, including the United States." Although the New People's Army professes Maoist principles, Marcos said, "we are certain" the money "is not from China."

Diplomatic sources said it was the first time Marcos had mentioned a foreign source of support for the New People's Army.

Marcos stressed that "they're not getting too much" and that the amounts were in the thousands of dollars rather than the millions. He said the other main rebel group, the Moro National Liberation Front, was no longer receiving foreign aid for its secessionist war in the southern Philippines and was weakening.

Marcos conceded that because of development problems, some parts of the Philippines were fertile ground for rebel groups. This recognition apparently lies at the heart of an ambitious new rural development program that seems to have become a top priority.

Certainly, the country's economic problems provide ammunition for the radical opposition. Real wages are declining, economc growth is slower, the balance of trade is worsening, and the foreign debt has reached $15 billion, near its constitutional limit.

About 25 percent of the work force is unemployed or underemployed, poverty and malnourishment are widespread, the disparity in incomes is widening and prices for the main export crops are way down.

Despite such problems, Marcos insisted, "the basic conditions for a revolution just aren't there."

One who disagrees is Spanish-born Roman Catholic Bishop Jose Querexeta, who has lived in the Philippines since being expelled from China shortly after the 1949 revolution there.

"People say I am pessimistic, and maybe I am," he said at his residence on the southern island of Basilan. "But I see now in the Philippines the same signs of frustration and despair that I saw among the masses in China 32 years ago when the communists took over."

"Unless drastic reforms are introduced in the country so wealth is not controlled by a few, the '80s can be a very dangerous decade," he said. Without such measures to distribute wealth more evenly, Querexeta added, "I think a revolution is inevitable."

In Manila, Cardinal Jaime Sin, the Roman Catholic primate and a persistent critic of the Marcos government, said, "We are trying to do everything we can to stop any bloody revolution."

According to Sin, "The president is against communism, but because of the way he is running the country the people are becoming more radical day after day and the moderates are disappearing." He said he was encouraging the legal opposition to "start oiling your mechanism" to better compete with Marcos.

"Maybe the time will come when the opposition will win," he said, citing the example of French Socialist Francois Mitterrand's presidential victory after repeated failures.

However, opposition politicians seem to despair of any change in government through the democratic process.

"More and more people are becoming convinced that short of an act of God, there is no way to get Marcos out and restore freedom in the country," said former senator Jose Diokno, chairman of the Civil Liberties Union of the Philippines. "This hopelessness has made the Communist Party of the Philippines the best organized party politically outside the government."

"My major concern is that we in the opposition don't seem to have a direction," he added. "The political opposition does not seem to be able to take advantage of Marcos' weaknesses."

Another opposition leader, former senator Gerardo Roxas, said in an interview before he left for cancer treatment in the United States that "we are for peaceful change, but we're slowly being edged out of the picture. If we are unable to bring about peaceful change, then the confrontation will be not between Marcos and the democratic opposition, but between Marcos and the left."

Roxas asserted that leftists "are certainly gaining ground in many parts of the country."

The opposition has charged that Marcos used his position during more than eight years of martial law, which he declared in 1972, to build a political machine that evolved as his New Society Movement. Since he lifted martial law in January, Marcos seems to have relaxed the authoritarian nature of his rule somewhat, but his opponents still find plenty of reasons to excoriate him.

For example, the press is freer than it used to be, but restrictions remain and criticism of Marcos is still not tolerated. Human rights abuses by the military are generally said to have diminished, but critics allege more excesses than ever by government-backed civilian groups waging counterinsurgency campaigns.

Other major opposition accusations are that Marcos and his supporters have remained in power after the lifting of martial law by resorting to voting fraud and other irregularities to win elections and plebiscites. In particular, they challenge the referendum earlier this year that approved constitutional changes, allowing Marcos to run for a new six-year term as president in a French-style quasi-parliamentary system of government. He also will be eligible for reelection.

Besides these changes, however, diplomatic sources also cite the opposition's own disarray as a reason for its troubles. While opposition politicans have excelled at criticism of Marcos and his policies, they have been unable to agree on alternative programs.

Specifically, diplomats said the United Democratic Opposition umbrella group never released a 28-page economic program it said it had prepared at the time of the June presidential election, apparently because of basic disagreements on the participation of multinational companies here.

Since then, further squabbles have erupted about the wisdom of the electoral boycott, leaving Marcos to garner 88 percent of the vote against token opposition and claim a new mandate.

Although Marcos explained his call for a stronger legal opposition as a way to curb financial abuses by members of his ruling party, political observers said it was also in his interest to counter the growth of the left.

"I realize there is a need for an opposition, especially when the majority party is very powerful," Marcos said. "You can't watch everything that happens in the government."

Marcos seemed sensitive about the idea of political polarization, calling it a "pure concoction." He also reacted strongly to the thesis that the Reagan administration is unwittingly furthering such a process by strong statements of support. Most often cited in this connection is the remark by Vice President Bush at Marcos' inauguration that "we love your adherence to democratic principles and to democratic processes."

Marcos said U.S. leaders "certainly don't influence the results of elections in this country, nor the feelings of our people." The idea that Bush's "ceremonial gesture" is "supposed to upset the political situation in the country is a little bit overdone. It not only offends me, it offends many other people. I don't owe my present position to anybody in the United States. Neither does anybody in the legislature , nor do the rebels."

Marcos was equivocal when asked if his call for a stronger opposition meant that his leading political foe, former senator Benigno Aquino, could return without being jailed. Under prodding by the Carter administration, Marcos freed Aquino in May 1980 after nearly eight years in prison to undergo heart surgery in the United States. Aquino decided to stay, taking a fellowship at Harvard rather than come back to finish serving his sentence on charges of subversion and murder.

Marcos said Aquino "has to answer to the Supreme Court" but he "would consider" granting a pardon.

Apparently recognizing that new development efforts are needed to counter growing disaffection among the rural poor in some areas, the government is promoting its ambitious "national livelihood movement" to create jobs.