HONG KONG — China's Communist Party has haunted Leung's family for generations. Her father, Guo Yao, fled forced labor and the violent purges of the Cultural Revolution for a better life in Hong Kong, where he arrived with his wife in 1973 to find relative freedom and prosperity. Years later, as his family watched the ceremony marking Hong Kong's 1997 handover from Britain to China, his then-teenage daughter had a premonition. “I thought to myself, maybe one day we will have to run away from the Chinese Communist Party again,” said Leung, now 36. “I just didn’t imagine it would...