BEIJING — The Rev. Jin Mingri peered out from the pulpit and delivered an unusual appeal: "Please leave," he commanded his flock, which was packed standing-room-only on a Sunday in a converted office space in China's capital. "We don't have enough seats for the others who want to come, so, please, only stay for one service a day."

Christianity — repressed, marginalized and, in many cases, illegal in China for more than half a century — is sweeping the country.

By some estimates, Christian churches, most of them underground, now have roughly 70 million members, as many as the Communist Party itself. A growing number of those Christians are in fact party members.

Christianity is thriving in part because it offers a moral framework to citizens adrift in an age of Wild West capitalism that has not only exacted a heavy toll in corruption and pollution but also harmed the global image of products "Made in China."

At the same time, Christianity is driving citizens to be more politically assertive. For decades, most of China's Christians worshipped in underground churches for fear of arrest.

But in scores of interviews for a joint project of the Chicago Tribune and PBS' "Frontline/World," clerical leaders and worshippers from coastal boomtowns to inland villages publicly detailed their religious lives for the first time.

They repeat a seemingly shared belief that the time has come to proclaim their place in Chinese society as the world focuses on China and its hosting of the 2008 Olympics, set to begin in August.

FAITH AND ETHICS

Christianity is spreading from poor villages to urban power centers with often tacit approval from the regime. Intellectuals disillusioned by the 1989 crackdown at Tiananmen Square are placing their loyalty in faith, not politics; tycoons fed up with corruption are seeking an ethical code; and Communist Party members are arguing that their faith does not put them at odds with the government.

The government is permitting churches to be more open and active than ever before, signaling a new tolerance of faith in public life. President Hu Jintao even held an unprecedented Politburo "study session" on religion last year, in which he said "the knowledge and strength of religious people must be mustered to build a prosperous society."

Today the government counts 21 million Catholics and Protestants — a 50 percent increase in less than 10 years — though the underground population is far larger.

The Rev. Jin did not set out to be a religious pioneer. From a secular family, he attended the elite Beijing University and joined the Communist Party.

In his junior year, the People's Liberation Army ended weeks of pro-democracy demonstrations in Tiananmen Square, leaving hundreds dead and shaking the faith of young intellectuals like Jin who had placed their hopes in the state.

Christianity offered an alternative to China's political orthodoxy. To those in search of something new in which to believe, the church promised salvation, moral absolutes and a sense of being part of an enterprise larger than China.