The governor of Isabela province, Grace Padaca, looked out at the misty rice fields from the tiled terrace of her official residence and said she never expected to call the mansion her home.

But Padaca, 40, a former radio commentator, was elected in May, upsetting Gov. Faustino Dy Jr., the third successive member of the powerful Dy family to run the province dating back 35 years. Dy had erected the white, Mediterranean-style villa on a hilltop shortly before the last election. "He thought he was building it for himself," Padaca said with a sly smile, "but actually, he was building it for me."

Padaca's victory not only broke the power of Dy's family over most of the key posts in Isabela but also exposed cracks in the dynastic system of government that has long characterized the Philippines at provincial and national levels. Padaca achieved her victory by stumping from morning to midnight across the impoverished villages of Isabela with a handful of volunteers, showing little sign of being slowed by a bout of childhood polio that leaves her using crutches.

"The Isabela experience says the dynasties are vulnerable," said Ramon Casiple, executive director of the Institute for Political and Electoral Reform. "The reality is that in more and more places, dynasties are being challenged and defeated. But this is not to say that the dynastic system itself is losing because there are also new dynasties coming in."

Family political dynasties remain the rule -- from the north, where the son of the ousted dictator Ferdinand Marcos continues to govern Ilocos Norte province, to the southernmost island of Mindanao, where traditionally powerful families retain control despite a challenge by Muslim rebels. The change in Isabela was one of several notable setbacks this spring for ruling families, including reversals in the urban outskirts of Manila and on the trading island of Cebu.

The system of family dynasties is rooted in U.S. colonial rule a century ago, when suffrage was initially given only to those Filipinos with property and education, offering the landed aristocracy a monopoly on power in the provinces. The Americans also put in place a U.S. system of congressional districts, which encouraged individual families to build local fiefdoms, rather than an electoral list system that could have fostered more competition.

For example, President Gloria Macapagal Arroyo, reelected in May, is the daughter of a former president. Her son and brother-in-law won congressional seats in the last election. Even the hero of the 1980s democracy movement, former president Corazon Aquino, was a product of the one of the country's mightiest political families. This year, five of her relatives were reelected to Congress and one to the Senate.

"Some dynasties have made positive contributions, but by and large the dynastic system in the Philippines has stunted the growth of real democracy," Casiple said. "It is not representative of the broad majority in any place."

In Isabela, the country's second-largest province in area, the Dys established themselves in trucking, prospering from the region's lucrative logging trade. The family patriarch, Faustino Dy Sr., was governor for 22 years.

When he retired, he turned the post over to one son, who in turn made way for another, Faustino Jr., in 2001. Eight Dy children entered elective politics and, even as the governor was losing in May, four of his brothers were winning reelection to various offices, including Congress.

Critics said that the Dy family had left the province underdeveloped, with less than half the farmland irrigated and businessmen reluctant to invest. They also said that though the area is a major producer of rice and corn, nearly all the crops are produced for export. There has been no development of local food processing industries, which could have created jobs, they said.

Dy family members counter that the younger Dy's tenure was the most progressive in the province's history. They point to the construction of more than 1,000 classrooms and a new public insurance program for hospitalization.

But the people of Isabela were looking for more. "There was a fear that the Dys have been here so long and they were going to gobble up the whole province unless someone did something," said Bishop Sergio L. Utleg of the Ilagan diocese.

That someone was Maria Gracia Cielo Padaca, a slight woman with intense brown eyes who had championed the causes of the poor for 14 years as a local radio commentator.

The daughter of school teachers, she said she discovered the world from books while other children played outside. Later, she said, she chose a radio career because she could reach the public while keeping her disability out of sight.

But her wish to remain invisible was outweighed by her sense of outrage at the Dys' monopoly on power.

"For people who think and people who care, it's insulting. I couldn't accept it," Padaca said. "But I thought I couldn't win. I knew it wouldn't ever be enough to defeat the Dys."

This spring, all but three of the 36 mayors in the province lined up with the incumbent. Many of her supporters declined to be seen with her in their hometowns, fearing they could lose their jobs. Mayor Caesar Dy of the town of Cauayan and more than 50 police officers raided Padaca's former radio station on the morning of election day and literally pulled the plug, according to the station manager, Charmy Sabigan.

Fearing widespread vote fraud by the Dys, the Catholic Church deployed about 3,000 parishioners to help guard the ballot boxes, Utleg recounted. He said officials aligned with the Dy campaign tried to falsify the returns in two towns, but the monitors maintained their own counts and successfully appealed to the election commission.

Padaca, who had built a loyal following from her years on the air, maintained a torrid campaign pace, traveling to more than a dozen villages each day in a borrowed truck, capping each evening with a midnight rally. On election day, she defeated Dy decisively.

His brother, Mayor Napoleon Dy of Alicia said in an interview that his family had not sought to cheat but instead accused communist guerrillas of intimidating voters on Padaca's behalf.

Political families are going through generational changes as incumbents increasingly arrange for successors from among their kin, fueled by recently adopted term limits on elected officials, Casiple, the reform institute director, said. A majority of newcomers to Congress continue to be members of political clans, according to a study this year by the Philippine Center for Investigative Journalism.

But Casiple said that some sons and daughters prove to be weak politicians, opening the door for challengers from outside the family.

As a single woman, Padaca said she is not about to launch a new dynasty in Isabela. It's not even clear that she will survive her three-year term. Padaca said her government is still packed with Dy loyalists. After she transferred eight department heads, they went to court last month to block her.

Provincial mayors recently voted Napoleon Dy as the chairman of their league. In an interview, Dy said the mayors would begin to rally public opinion against her, in particular publicizing what he called her failure to provide adequate public services.

In an interview at the governor's mansion, Padaca admitted that winning may prove easier than governing. But motioning to her metal crutches resting against a wall of the terrace, she said she is tougher than most in the province imagine.

"My weakness is my strength. My opponents underestimate me and don't know what hit them," she said, her voice growing thick with emotion.

Suddenly, softly, she began to cry. An aide handed her a paper napkin to dab her cheeks.

"I tell people, 'Don't take pity on me. I can take care of myself. Take pity on yourselves. You are still poor after 40 years of this dynasty,' " she said. "I tell them they don't have to be imprisoned all their lives."

Grace Padaca, the new governor of Isabela province, sits at the official residence built by her predecessor, a member of a political dynasty.