HONG KONG — A string of scandals involving both the current leader of Hong Kong and those vying to succeed him is threatening to stain what many residents here consider a source of pride: a city largely free of corruption.

The accusations confronting Donald Tsang, the chief executive of Hong Kong, and two of the candidates underscore deep-seated fears that a small circle of tycoons has come to dominate the top levels of government almost 15 years after this former British colony reverted to Chinese rule. Many worry that the city’s tradition of transparent rule of law may be giving way to how business and politics are conducted in mainland China.

“This may be the accepted practice in China, but it’s not permitted in Hong Kong,” Fung Chi-wood, an Anglican pastor and former legislator, said of local news reports that Mr. Tsang accepted favors like rides on yachts and jets and negotiated a below-market rate for a luxury apartment from wealthy businessmen. Mr. Fung was among thousands of people who demonstrated last weekend against the influence of the rich in local government. “We are afraid our standards are becoming lower,” he said.

The scandals also point to what analysts say is the driving issue in the March 25 election: Hong Kong’s relationship with the mainland. Residents are asking whether the integration that has taken place since 1997, making the city more prosperous than before, may also be diminishing the territory’s quality of life.