Marcos, 80, will run in next May's elections as a candidate for the northern Illocos Norte constituency, a Marcos family stronghold.
The local, provincial and national elections will see around 17,000 seats decided by the 45 million eligible voters.
Arroyo, who steps down as president next year, registered as a candidate earlier this week, making her the first president of the Philippines to run for a seat in the lower house.
Because the constitution forbids her from running for president again, her many critics have accused her of still hankering for power.
Arroyo is the most unpopular president since Ferdinand Marcos, who was ousted by a popular uprising in 1986 after 20 years in power. The Marcos family went into exile in the United States until 1991 when Imelda returned to the Philippines. She then ran for Congress, serving from 1995 to 1998.
The family has often been accused of running a fiefdom in Illocos Norte on Luzon Island at the northern tip of the Philippines. Imelda is attempting to replace her son Ferdinand Marcos Jr. Nicknamed Bong-Bong, he is running for the Senate. His sister Imee is running to be governor of Illocos Norte, the birthplace of her father.
A report in the Manila Times noted that Arroyo told her supporters in her home province of Pampanga that she was not ready to leave politics. "So I have decided to respond affirmatively to your call," she said at a rally in the small farming town of Lubao.
"We have gone too far and too much is at stake now for us to waver in my commitment to the nation," said Arroyo, who became president in 2001 after Joseph Estrada was ousted in a bloodless coup.
However, the Manila Times report suggested that the influential Roman Catholic Church is wary of her plans if she is elected. They believe she might want to become prime minister through the back door by altering the constitution.
Estrada himself has come out demanding that Arroyo resign from the presidency now, saying she is "diminishing the stature of her office with her decision to run for a seat," according to a report in the Philippine Daily Inquirer.
He said she also has an undue advantage over her opponents as a sitting president. "She has all the government resources," he is quoted as saying. "I pity her opponents who will have no chance."
Also in the electoral ring, again, is the seven-times world boxing champion Manny Pacquiao. He is running for the second time after a defeat in the congressional election of 2007. Pacquiao won a fifth world boxing title last month, making him a victor in five weight classes. He beat Miguel Cotto to take the WBO's welterweight crown.
Pacquiao filed his candidacy in the town of Alabel in the province of Sarangani on Mindanao Island, at the southern extreme of the Philippines and a Muslim-majority area noted for kidnappings and civil unrest.
Pacquiao is running under his own banner the People's Champ Movement and told local media that he wants "only good things" for Sarangani. "I will work for children, for the health of our countrymen and for their livelihood."
The semiautonomous Mindanao was declared under emergency rule last week by Arroyo after the mass murder of 57 people who were on their way to register their candidate for local elections. Police have charged the son of a local clan leader with the slayings.
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