As her minibus known as the "Cory-van" slowly eased through a crowd of supporters, Corazon Aquino suddenly threw open a window and reached out to the cheering throng. A crush of people, adulation on their faces, practically enclosed the vehicle as supporters strained to grasp her hands or touch her.

"This is a flesh-to-flesh campaign," said Lupita Kashiwahara, the sister-in-law and press aide of the opposition presidential candidate. Buoyed by the large, responsive crowds that greet Aquino almost everywhere she campaigns in her electoral crusade to unseat President Ferdinand Marcos, the 53-year-old widow is "working toward a landslide" to overcome expected cheating in the Feb. 7 election and ensure a margin for victory, Kashiwahara said.

Whether or not this happens, it is clear that Philippine politics already have changed dramatically and that the widow of assassinated opposition leader Benigno Aquino Jr. will have a key role to play no matter who wins the election.

From a self-described "ordinary housewife" with no political experience, "Cory" Aquino has emerged in the two months since she declared her candidacy on Dec. 3 as not only a credible presidential contender but as the strongest challenger to Marcos in his 20 years in power. In fact, in a number of surveys and in the minds of many Filipinos, she is no longer the underdog but the clear favorite to outpoll Marcos on Friday.

Yet, many opponents of Marcos -- including Aquino -- do not expect the opposition to be able to take office after the election even if Marcos loses at the polls. Marcos still has cards to play that can keep him in power, they say, and rules for a transition have not been defined clearly.

Asked in an interview Wednesday whether she believed that Marcos, having occupied the Malacanang presidential palace for 20 years, actually would give up power even if he clearly lost the election, Aquino replied quietly, "I guess not."

She added, however, that "there's something unique in these elections, in that there is now a personal commitment on the part of so many Filipinos. It's not only time and money, but really risking their businesses or their lives. It's really a do-or-die situation now. So many have realized that this is our moment of truth, and they just have to give their all now or that chance may never come again."

Much depends on the arithmetic of the election and of voting fraud, Philippine-style. A major source of hope for the opposition is that, as one Marcos campaign official candidly put it, "mathematically, you can only cheat so much."

As the election approaches, the rival camps have launched a "battle of the polls" in which each claims a clear lead. Accompanying this has been a dispute over a "quick count" -- a running tally from around the country -- between the Marcos-appointed Commission on Elections, the official body responsible for overseeing elections, and the National Citizens Movement for Free Elections, a civic poll-watching group known as Namfrel.

According to the Roman Catholic Church-backed newspaper, Veritas, 14 straw polls held in schools and parishes in the capital -- before the Marcos government suddenly suspended classes for 10 days on Jan. 27 -- showed Aquino an overwhelming winner by a margin of more than 47 percent. However, other straw polls and opinion surveys publicized by the government put Marcos well ahead.

An independent poll conducted privately by a wealthy businessman with connections to both sides showed Aquino leading Marcos 60 percent to 40 percent nationwide as of Jan. 30. However, according to the calculations of the pollster, whose surveys are considered credible by diplomats, this margin may not be enough to ensure victory for Aquino if the political machine of Marcos' ruling New Society Movement is able to employ ghost voters, intimidation of opposition supporters, massive switching of election returns and other anticipated means of fraud.

The strategy of the Aquino camp thus is to run up such a big early lead that the Marcos machine will become demoralized and give way to an opposition bandwagon. But that is largely dependent on early results becoming known, hence the government's efforts to sandbag Namfrel's plans for an "operation quick count." The official Commission on Elections has insisted that it control any such operation.

Aquino has said that she plans to lead massive demonstrations if the election is stolen from her, but she acknowledges that the goal of ousting Marcos through public protests may be difficult to achieve in a peaceful manner.

"We would have to do something," she said, "and this is the only language that Marcos understands. I can't say that we'll just sit quietly and applaud Mr. Marcos for cheating us again."

"If I even dare hint that 'let's do away with Marcos,' these people are just so primed up to hear the battle cry," Aquino says of her supporters, that "I have to be very careful with my choice of words."

The transition from housewife to presidential candidate to potential mass demonstration leader represents a phenomenal metamorphosis for the retiring mother of five who has never before run for office.

Born Jan. 25, 1933, in Manila, Corazon Cojuangco Aquino grew up as the sixth of eight children in a family of wealthy landowners in Tarlac Province, about 70 miles north of the capital. After attending exclusive grade schools, she went to the United States in 1946 to continue her secondary education at Ravenhill Academy in Philadelphia, Notre Dame convent school in New York and the College of Mount St. Vincent in New York.

There, in 1953, she earned a degree in French and Mathematics. She returned to Manila to study law and met Benigno Aquino, an aspiring politician whom she married in 1954. For years she stayed in the background as the quiet, reserved wife of the gregarious and ambitious Aquino, who seemed destined to become the Philippines' president until he was arrested in 1972 just hours after Marcos declared martial law. He remained in prison until 1980, when Marcos allowed him to seek heart treatment in the United States.

Corazon Aquino often has described the next three years, when her husband was a fellow at Harvard and Massachusetts Institute of Technology, as the happiest in her life, because of the family's togetherness. After her husband returned to Manila and immediately was assassinated, a killing she says was ordered by Marcos, Aquino reluctantly became a public figure as she sought to keep her husband's ideals and memory alive.

But when a divided moderate opposition began turning to her last year to assume her husband's role as a unifying figure, she repeatedly ruled herself out as a presidential candidate. It was only after Marcos called a special election and supporters gathered a million signatures on a petition for her candidacy that she decided to run for president.

Initially, Aquino was expected to play a unifying role, and, if elected, she was to have become a figurehead president and allow a collective leadership of opposition politicians to run the country. But since she became the single presidential candidate of the opposition, with erstwhile rival Salvador Laurel running for vice president under her, Aquino has taken more forceful positions on exercising leadership.

The first woman presidential candidate in the Philippines, Aquino has declared that she would assume leadership of the armed forces and would not allow herself to be "manipulated" by her advisers.

"I have already proved that I cannot be manipulated by anybody," she said in the interview Wednesday. She noted that she was able to resist a series of conditions originally imposed by Laurel in exchange for his agreement to give up his own presidential candidacy.

"I would be a dummy president" if the nine conditions had been accepted, Aquino said. "Why should I bother being a candidate?"

Despite all this, Aquino said the effort has been worth it, even if the election eventually is stolen. "They tell me I have inspired so many people," she said. "If only for that I think it would have been all worthwhile."