Cardinal Jaime Sin, the powerbroker at the heart of Philippine people power revolts, was rushed to a Manila hospital on Monday after reportedly suffering a heart attack, church officials and local media said.
Sin, who retired as Archbishop of Manila last November due to poor health, was taken to hospital late in the afternoon.
A church photographer, Noli Yamsuan, said he had been told by one priest that Sin was in a stable condition.
But a Roman Catholic bishop who asked not to be named said Sin was in a "50-50 condition."
Local radio said he had suffered a heart attack.
Sin, 76, was once called "the divine commander-in-chief" by former president Fidel Ramos, a protestant, for marshalling huge protests in the mostly Roman Catholic country that drove presidents Ferdinand Marcos and Joseph Estrada from office in 1986 and 2001, respectively.
"My duty is to put Christ in politics. Politics without Christ is the greatest scourge of our nation," Sin said at his retirement ceremony.
Sin had a brief spell in hospital last year after suffering a seizure while at prayer. He has a long-standing kidney ailment. His departure signaled the end of an unprecedented period of political activism by the church, although it remains a potent force and a key backer of President Gloria Macapagal Arroyo.
"Oh my, I pity him. I will pray the rosary for him. I hope he makes it," said Segundina de Castro, 70, a devout Catholic from central Mindoro island.