Philippine business leaders who feel their country or companies can never prosper under the "crony capitalism" of President Ferdinand Marcos have taken on the risky roles of advisers and financial backers of his opponent in Friday's presidential election, Corazon Aquino.

Out front is a corps of executives-turned-street activists.

Behind them, anonymous for the most part, are lunch-club colleagues who have kept the campaign moving with cash and gifts, including office space, placard paper and helicopter rides.

Confronting Marcos does not come easy in a country where business has generally sided with the status quo and a presidential decree can make or break a company. Many are fearful of retribution if Aquino loses.

But many indicate the key to turning around a 2 1/2-year economic crisis that has already pushed many businesses into bankruptcy is showing the door to Marcos, now in his 21st year in the presidential palace, and his associates.

"They look on the Philippines as private property," says Ramon R. del Rosario, a Harvard-educated bank president and top adviser to the Aquino campaign.

Gauging the stance of the business community as a whole is difficult. But western analysts commonly see it as polarized into "the cronies," a small group of Marcos' associates who have prospered with special privileges and financing awarded by the palace, and everyone else.

Aquino's camp blames much of the country's economic crisis on "crony capitalism." This group says billions of development dollars have been squandered through mismanagement and corruption by Marcos' team and illegally sent abroad to banks accounts and real estate investments.

Those outside palace circles, they say, often cannot get permits and financing for new projects. Even if they do, they are reluctant to do too well, lest they attract the attention of a crony and get taken over.

Marcos' supporters contend that the crisis has nothing to do with the presidential associates. They put blame on political agitation following the 1983 assassination of Aquino's husband, opposition leader Benigno Aquino Jr., and events in the world economy, primarily a fall in prices for commodities on which the country depends for much of its export earnings.

That many business leaders do not agree was made clear yesterday, when Aquino stepped into a chandeliered ballroom at the Manila Intercontinental Hotel for a lunch sponsored by the country's major chambers of commerce. The 2,000 people packed inside gave her a thunderous ovation.

In introductory remarks, praise was heaped on her by Felix K. Maramba Jr., former president of the Philippine Chamber of Commerce and Industry. He is also a flour miller who recently tangled with an associate of Marcos who wanted to take control of the milling business.

Aquino's speech, in which she pledged to clean up the economy "with the zeal of a crusading housewife let loose in a den of world-class thieves," was interrupted by applause more than 35 times.

Marcos addressed the same forum today. His reception was chillingly proper. He got only polite applause even when, as the group watched, he signed a collection of presidential decrees giving business leaders bits and pieces of what Aquino had proposed the day before.

Although Marcos alleges Aquino is linked to Communist insurgents here, her economic program seemingly could be drawn from lessons by President Reagan and British Prime Minister Margaret Thatcher.

Born into one of the Philippines' landed families, Aquino is described by those close to her as a conservative and religious nationalist. The key to reviving the economy, her platform says, is getting government and the palace out of business promptly.

Business supporters have brushed aside her lack of experience in government and listened with approval to her promises to dismantle the crony privileges, deregulate and sell off to the private sector many of the state-owned banks and companies, whose numbers have grown to about 250 under Marcos.

Rather than socialism, the fear in business circles about Aquino seems to be more that she would turn out as just another autocrat and simply transfer power from one group of families to another.

In her speech, Aquino repeated a pledge to break up monopolies in coconuts and sugar that are controlled by Marcos' associates. She promised to put money into agriculture, by which most Filipinos still make their living, and repeal special taxes on energy and businesses sales on the grounds they are regressive.

She pledged to renegotiate foreign-debt payments and to put off an import liberalization program demanded by the International Monetary Fund as a condition of credit support. The latter step would be welcomed by businessmen, who feel they cannot compete with foreign products, especially in a time of crisis.

Aquino concedes she knows nothing about economics. But businessmen are heartened by the fact that her closest adviser in the field is a respected member of their community. He is Jaime V. Ongpin, president of the Benguet Corp., a mining concern that was the Philippines' 18th largest company in terms of revenues in 1983.

Signs of long-term trouble in debt and productivity began appearing in the Philippines economy in the 1970s, setting the stage for a full-blown panic after the 1983 murder of Benigno Aquino as he stepped off a plane at Manila airport after returning from political exile.

Since then, the Philippine economy has shrunk in real terms by about 10 percent. Factories have closed, foreign and domestic investment has come to a near standstill and the government has had to reschedule its $27 billion in foreign debt.

The push into politics for members of the business community began with the killing, which many people here blame on Marcos. If you make trouble, "we'll kill you -- that was the message," says a woman from a prominent family here.

Mass marches against Marcos began snaking through the Makati district, Manila's equivalent of Wall Street, and executives wandered down from high-rise offices to join. Some got a taste of tear gas and gunshots fired overhead by riot police.

Last summer, following charges that Marcos secretly made large personal real estate investments in the United States, a coalition of major business associations, in a gesture hardly friendly to the president, printed ads in newspapers calling for a full investigation. "Above all, we are concerned with the morality of these investments," an ad said. Marcos has denied owning any such real estate.

Ongpin says that most of Aquino's funding comes from business rather than mass fund-raising. It often arrives in cash because of fears of tracing and retribution by the government. "Many of them don't even want the opposition to have it in their records," he says.

Ongpin says 90 percent of those he has approached have given. "About the only people who aren't contributing are the ones who are on the verge of collapse," he says.

He declines to put a figure on the spending, noting it is very "sensitive." Philippine law limits total spending for the campaign to around $2 million.

Del Rosario says his business has not been the target of harassment by the government. But Ongpin says his has been denied mining licenses it deserves.