Philippine President Ferdinand E. Marcos will probably defeat his challenger Corazon Aquino in the upcoming presidential elections, but it is likely that he will die in office, leaving the country in chaos, Harvard experts predicted yesterday.

Although Aquino and her supporters throughout the United States and the Philippines are working hard to prevent Marcos's re-election, control of the country's political and military resources will remain in the hands of his dictatorial government, said MacArthur F. Corsino, former Philippine minister of foreign affairs and a fellow at Harvard's Center for International Affairs (CFIA).

Corsino, 10 days ago, became the third Philippine foreign service official to resign his post within the last month to protest the Marcos regime. Corsino said yesterday he had to step down because "in conscience, I could not envision myself serving under Marcos's regime" and because he and others want to give moral strength to Aquino supporters.

Marcos, 68, has ruled for 21 years. He suffers from a kidney condition and has for years been reported to be very ill.

"President Marcos is quite sick," Corsino said yesterday. "We don't now how long he will last. The time for a peaceful, non-violent transition is now."

"If there are conflicting claims of victory following this week's election, there is danger of widespread chaos and anarchy," Corsino added.

Election

Experts, such as CFIA Director Samuel P.Huntington, predict that the February 7 electionitself will not bring down Marcos's regime.

Huntington said Marcos is likely to remain ashead of state for any one of three reasons. Hecould win a fair election because the bulk of therural Philippine population supports him. Marcosmight manufacture votes and not let Aquino win.And even if she does win, Marcos might declare astate of emergency and invalidate the results ofthe elections, Huntington said.

"The probablility of any of these thingshappening is far greater than the possibility ofvotes being counted fairly, and Aquino beingallowed to rule the Philippines," he added.

Undaunted

Aquino supporters, convinced that theircandidate will win if the elections are fair, havebeen working to publicize Marcos' ill health inorder to undermine his image as a powerful andeffective leader among the people of thePhilippines, Corsino said.

Support for Aquino is especially strong in theBoston area, where her husband, the slainopposition leader Benigno S. Aquino Jr., spentthree years in self-imposed exile. During two ofthose years, the resistance figure was a fellow atthe Harvard Center for International Affairs,before returning to the Philippines, where he wasshot to death August 21, 1983.

In addition, Philipino-American groups haveattempted to spread American media coverage ofMarcos's dubious war-hero stories, his allegedsecret $100 million in New York real estateinvestments to the Philippines and otherinformation suppressed by the Marcos regime.

But Corsino said Aquino activists "cannot beoptimistic about the results of the election,"because of the "network of fraud" already inplace.

Chaos

But if Marcos is re-elected and then suddenlydies, the struggle for succession could be verybloody, Corsino said.

A study by Huntington and Richard K. Betts, avisiting professor and fellow at theWashington-based Brookings Institute, agreed. Aslong as Marcos remains in power, his moderateopposition will gradually decline, and moreradical insurgent groups will gain support,Huntington said.

"The character of post-Marcos instability willdepend on the extent to which the democraticopposition is able to cohere around a leader and aprogram," the study said.

In order for Aquino to be elected, according toCorsino, the U.S. government must take a strongerstand against the Marcos regime. President Reaganhas declared his support for whichever candidatethe Philippines chooses by "free and fairelections.