SEVEN YEARS AGO tomorrow Hong Kong returned to Chinese rule with both fanfare and fear. The freewheeling city-state had evolved during its decades as a British colony into an exemplar of capitalism and the rule of law, and optimists hoped that some of its magic might rub off on Communist China. The pessimistic view was that influence would flow the other way, with China's corruption and one-party authoritarianism gradually eroding Hong Kong's freedoms. Lately Beijing has been turning the pessimists' view into reality, to disturbingly little complaint from the United States and other democracies.

The most visible blow came when Beijing rejected any possibility of popular elections for Hong Kong's chief executive in 2007 and for all legislators in 2008. But also damaging are the continuing manipulations by Beijing of Hong Kong politics and media. This year Chinese officials labeled pro-democracy leaders "unpatriotic," setting a tone for the harassment and intimidation that duly followed. Already, three outspoken radio talk-show hosts have quit after receiving what they alleged were threats from people with ties to the Chinese government. A pro-democracy lawmaker's office, previously vandalized with excrement, was set on fire overnight last week with a threat scribbled on the wall: "All Chinese traitors must die."

Much of the intimidation is related to September elections. Hong Kong operates under a system that allows voters to choose half of its legislators, while others are selected by professional associations more easily manipulated by Beijing. But even that degree of control is not sufficient for mainland China. Voters are being pressured by employers and others to back pro-Beijing candidates and encouraged to photograph marked ballots with cell phone cameras to prove their patriotism. Provoking fears of even more blatant interference, two Chinese public security agents were found operating in Hong Kong, while mainland authorities refuse to say what they were doing there.

Beijing officials seek to balance their bad-cop tactics with a good-cop strategy of boosting the territory's economy with aid. But Hong Kong is not, as sometimes caricatured, a city of businessmen who don't care about politics. Many residents resent Beijing's hard-line tactics. That much has been shown in the democrats' big win in local district elections in November, along with rising voter registration levels in advance of September's election. Hundreds of thousands are expected to demonstrate tomorrow in favor of democratization.

That such protests are permitted shows that Hong Kong remains freer in many ways than the rest of China. But if voter intimidation and ballot rigging mar September's election, it will lead to serious questions about the extent of Hong Kong's autonomy. The Bush administration, which so far has made only mild statements encouraging Beijing to "be responsive" to the people of Hong Kong, ought to vigorously condemn the tactics of voter intimidation and make clear that U.S.-China relations will suffer if the democracy and autonomy of the territory are further eroded.