BEIJING — “Thank you. I’m well. Don’t worry,” read the post on a Chinese social networking site. The brief comment, published in June, appeared to come from Ling Gu, the 23-year-old son of a high-powered aide to China’s president, and it helped quash reports that he had been killed in a Ferrari crash after a night of partying.

It only later emerged that the message was a sham, posted by someone under Mr. Ling’s alias — almost three months after his death.

The ploy was one of many in a tangled effort to suppress news of the crash that killed Mr. Ling and critically injured two young female passengers, one of whom later died. The outlines of the affair surfaced months ago, but it is now becoming clearer that the crash and the botched cover-up had more momentous consequences, altering the course of the Chinese Communist Party’s once-in-a-decade leadership succession last month.

China’s departing president, Hu Jintao, entered the summer in an apparently strong position after the disgrace of Bo Xilai, previously a rising member of a rival political network who was brought down when his wife was accused of murdering a British businessman. But Mr. Hu suffered a debilitating reversal of his own when party elders — led by his predecessor, Jiang Zemin — confronted him with allegations that Ling Jihua, his closest protégé and political fixer, had engineered the cover-up of his son’s death.