Winnie Greco, a top fund-raiser and senior adviser for Mr. Adams, has long had dealings with people and groups connected to China’s communist regime. He kept her close even so.

Linda Sun is just the latest member of the Chinese diaspora whom Beijing is accused of recruiting to influence Western democracies.

Linda Sun, a former deputy chief of staff to Gov. Kathy Hochul, used her growing influence to push the interests of the Chinese government, U.S. prosecutors say.