BEIJING — Behind the west Beijing apartment building where Liu Xia keeps a fifth-floor flat, the police have built a guardhouse. Its purpose is not to protect Ms. Liu, who seeks no safeguarding. The house is for the guards who watch her.

Inside, they take notes to record her comings and goings. When she ventures out, a guard picks up the phone. Soon, a sedan with darkened windows carrying a man with a telephoto-lens camera is trailing her.

During a recent chat in a nearby teahouse, Ms. Liu wondered aloud why she unnerves China’s rulers enough to merit her own guardhouse. She is not active in politics, she said, and does not even use a computer. “I take photos, paint paintings, write poems, read books, cook food,” she said with a mirthless laugh. “And drink.”

But, of course, she knows why. She is married to Liu Xiaobo, a writer, philosopher and democracy advocate. On Dec. 10, Mr. Liu and 302 others issued a manifesto, called Charter 08, that urged China’s Communist Party to abandon monopoly rule and establish a multiparty system of government.

The police seized Mr. Liu two days before Charter 08 was released. He has been locked ever since in a windowless room about an hour’s drive north of central Beijing. He is denied access to lawyers, to pen and paper and, exceptfor two brief visits, to his wife.

He is allowed to ask for books. His latest request was for the works of Kafka.

Perhaps Mr. Liu sees himself in Gregor Samsa, the Kafka protagonist who, transformed into a giant pest, is locked in a room in the hope that “out of sight” will become “out of mind.”

But his captors’ plight is also surreal. Signed by leading intellectuals, including some with links to the Communist Party, Charter 08 has been called the most important political statement since the 1989 Tiananmen Square protests.

Increasingly, Liu Xiaobo is no ordinary dissident, but an international cause. And the crackdown on him and his wife shows signs of becominga public-relations dilemma for Chinese leaders.

“If they don’t suppress this matter, its influence will keep growing,” said Zhang Zuhua, a political theorist who helped Mr. Liu and others draft the charter. “But the more they suppress it, the more its influence will grow.”

Mr. Zhang also has a police guard, and a sedan that follows him. He has been warned that he is under investigation and should not make political waves.

Charter 08 concerns party rulers, some contend, because it posits an alternative to their monopoly just as China is integrating with an overwhelmingly democratic world.

Among the 20 largest economies, China is alone in enshrining single-party rule in its Constitution. Russia and China both persecute political opponents. But only China is visibly agitated by Charter 08’s premises: that people should elect their leaders, divide power among government’s branches and make the military answerable to civilians.

“Freedom is at the core of universal human values,” the charter states. “The government exists for the protection of the human rights of its citizens.” And, it states, “The most fundamental principles of democracy are that the people are sovereign, and the people select their government.”

Mr. Liu and Mr. Zhang first drafted those phrases more than three years ago with about eight other friends. Their inspirations, Mr. Zhang said in an interview, were the Magna Carta, the Declaration of Independence, France’s 1789 Declaration of the Rights of Man and of the Citizen and Taiwan’s 1980s democracy movement.

Mr. Zhang says their goals are evolutionary, not revolutionary. Most of the signers witnessed the destruction of China’s last pro-democracy movement in Tiananmen Square in 1989; some, including Mr. Liu, were participants in that movement. “Twenty years later,” Mr. Zhang said, “we all think that China will head toward liberal democracy eventually. But the problem is that we cannot use such sacrificial means again. So how to find a better way toward democratization that’s more suitable to China’s situation?

“People must come up with a constructive view. That’s the main idea behind Charter 08,” he said.
Such manifestos are hardly new. In December 1978, the Fifth Modernization, a proposed liberalization of the political system to go with China’s other moves toward modernity, was posted on Beijing’s Democracy Wall — and its author was handed a 15-year prison sentence. Evidence of the document was wiped from Chinese history.

Whether Charter 08 and Mr. Liu will meet similar fates remains unclear. Thirty years later, party leaders appear equally determined to retain power, but more cautious about how.

Censors have deleted Charter 08 from Chinese-language Internet pages and chat rooms, and some Web sites publishing pro-charter bloggers have been shut down. Without mentioning the charter, party leaders have railed against multiparty democracy and separation of powers as Western-imposed “erroneous ideological interferences.”

Many of the charter’s original signers have been interrogated; some have lost prominent positions or, in one case, been transferred from Beijing to remotest western China.

Mr. Liu, the only signer to be detained, is officially under “residential surveillance,” suspected of inciting subversion. But his secret confinement, lacking even a written explanation, meets no legal standard, his lawyer said.

Mr. Zhang says the aim of the authorities is to smother the charter with a minimum of force and international outcry. “They make a very precise calculation,” he said. “If they can manage to suppress this matter by arresting only Liu Xiaobo, then that’s the best deal for them.”

Yet Charter 08 continues, slowly, to gain adherents. Mr. Zhang says considerably more than 8,000 Chinese citizens have joined the original 303 signers, representing a swath of society well outside theclique of political dissidents. Another tranche of signatures is imminent.

In Beijing, the police recently searched the flat of a man who printed T-shirts with Mr. Liu’s face on the front and “Charter 08” on the back. In Nanying, a central city of about a million, an oil refinery worker named Liu Linna handed out perhaps 100 copies of the charter on April 4 before the police seized her.

“Seeing how severely Charter 08 was blocked on the Internet, I could not stand it,” she said. “So I decided, if I can’t talk about it on the Web, then I must spread the word on the streets.”

Liu Xia says her husband passes his time in detention watching sports — his captors recently installed a television — and lying in bed, planning his legal defense. It is a familiar role. Mr. Liu spent two years in prison after the 1989 Tiananmen protests, and three years in a labor camp starting in 1996 for challenging single-party rule and advocating negotiations with the Dalai Lama over Tibet.

Liu Xia and Mr. Zhang meet weekly to play badminton. Their sedans follow them to the game and wait outside the court until they have finished. Then the automobiles follow them home.