THE DEAL UNDER which Chinese activist Chen Guangcheng left the U.S. Embassy in Beijing on Wednesday was bold, risky and potentially groundbreaking for human rights in China. It could also prove disastrous. By late Wednesday, Mr. Chen, who was then in a Beijing hospital, was telling Western news organizations that his decision had been forced by threats to his family and that he wished to exit China for the United States. That may or may not reopen a six-day crisis over his status. What’s clear is that the Obama administration now bears moral responsibility for Mr. Chen’s freedom and welfare.

The blind, 40-year-old activist aspired to be — and could still become — a model for Chinese who seek to promote the rule of law and respect for human rights. Having studied the checkered history of dissidents who found asylum in the United States, Mr. Chen told U.S. officials and his supporters that he wished to remain in China. His aim was to force senior government officials to end the illegal persecution of his family by authorities in his village and province and to allow him to continue his work as a human rights lawyer.

To their credit, U.S. diplomats in Beijing retrieved Mr. Chen after learning he had escaped from his village and brought him into the embassy — an act that infuriated the Chinese government. By early Wednesday, the diplomats believed they had brokered a bargain under which Mr. Chen would be reunited with his family and allowed to attend law school in another city. Were it to follow through on those promises, the regime would break with a pattern of relentlessly hounding dissidents and human rights activists, a number of whom have been illegally confined to their homes.

The progress this would represent, and Mr. Chen’s professed desire to remain in China, made the deal a risk worth taking. But it also put the Obama administration under obligation. Having strongly encouraged Mr. Chen to accept the Chinese offer, the administration must ensure that he is treated fairly — or appear naive and feckless. Already Mr. Chen’s supporters and human rights groups are suggesting that the Americans pressured him into a bad deal because of their desire not to disrupt a U.S.-China strategic dialogue that began Wednesday evening.

U.S. officials sound credible when they insist that Mr. Chen never asked for asylum and was never told that the lives of his family would be in danger if he did not leave the embassy. They were to meet with him again on Thursday, and they may learn whether he has changed his mind about leaving the country. If he remains, the test of U.S. mettle will come in the next weeks and months. If Mr. Chen is allowed to live freely, the Obama administration can claim credit for a human rights breakthrough. If not, the United States must defend him and his family — and not allow business as usual in U.S.-Chinese relations.