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 Ling’s alias — almost three months after his death.

The ploy was one of many in a tangled effort to suppress news of the Ferrari crash that killed 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 killing a British businessman. But 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 protege and political fixer, had engineered the cover-up of his son’s death.

According to current and former officials, party elites and others, the exposure helped tip the balance of difficult negotiations, hastening Hu’s decline, spurring the ascent of China’s new leader Xi Jinping and playing into the hands of Jiang, whose associates dominate the new seven-man leadership at the expense of candidates from Hu’s clique.

The case also shows how the profligate lifestyles of leaders’ relatives and friends can weigh heavily in backstage power tussles, especially as party skulduggery plays out under the intensifying glare of media.

Numerous party insiders provided information regarding the episode, speaking on the condition of anonymity for fear of reprisals from the authorities. Officials have investigated the aftermath of the car wreck, they say, including looking into accusations that a state oil company paid hush money to the families of the two women.

Under Hu, Ling Jihua had directed the leadership’s administrative center, the General Office, but was relegated to a less influential post in September, ahead of schedule. Last month, he failed to advance to the 25-person Politburo and lost his seat on the influential party secretariat.

Hu, who stepped down as party chief, also immediately yielded his post as chairman of the military, meaning he will not retain power as Jiang did.

"Hu was weakened even before leaving office," said a mid-ranking official in the Organization Department, the party’s personnel office.

Ling’s future remains unsettled, with party insiders saying that his case presents an early test of whether Xi intends to follow through on public promises to fight high-level corruption.

"He can decide whether to go after Ling Jihua or not," said Wu Guoguang, a former top-level party speechwriter, now a political scientist at the University of Victoria in British Columbia, Canada. "Either way, this is a big card in Xi Jinping’s hand."

Ling, 56, built his career in the Communist Youth League. At an early age, he secured the patronage of Hu, who led the Youth League in the early 1980s and brought Ling to the General Office in 1995.

"Hu didn’t come with a lot of friends, but Ling was someone he knew he could trust," said the Organization Department official. "Officials said that if Ling called, it was like Hu calling."

Ling played a central role in moving Youth League veterans into high offices and undermining Hu’s adversaries. Ling also wielded leverage over Internet censorship of leaders’ affairs and sought to use it to benefit his patron.

"Negative publicity, including untruths, about Xi Jinping were not suppressed the way publicity about Hu Jintao was," said one associate of party leaders.

As his influence grew, Ling tried to keep a low profile. About a decade ago, his wife closed a software company she owned and formed a nonprofit foundation that incubates young entrepreneurs. The couple sent their son, Ling Gu, to an elite Beijing high school under an alias, Wang Ziyun.

"Ling Jihua told his family not to damage his career," a former Youth League colleague said. "But it seems it can’t be stopped."

Still living under an alias, Ling Gu graduated from Peking University last year with an international relations degree and began graduate studies in education. One of his instructors said his performance plunged later in his undergraduate years.

"I think there were too many lures, too much seduction," he said.

Before dawn on March 18, a black Ferrari Spider speeding along Fourth Ring Road in Beijing ricocheted off a wall, struck a railing and cracked in two. Ling was killed instantly, and the two young Tibetan women with him were hospitalized with severe injuries. One died months later, and the other is recovering, party insiders said.

Under normal circumstances, party insiders said, suppressing such news to protect the image of the party would be a routine matter. But Ling Jihua went further, they said, maneuvering to hide his son’s death even from the leadership.

The Beijing Evening News published an article and a photograph, but the topic was immediately scoured from the Internet. Later, the families of the two women in the car received payments from China’s largest state oil company, according to a top executive with a major foreign multinational. He said the money was paid "to make sure they shut up." A publicity executive for the company, China National Petroleum Corp., declined to answer questions about the matter.

When overseas Chinese-language media reported in June that the Ferrari driver had been Ling Jihua’s son, the Hong Kong-based magazine Yazhou Zhoukan published a story debunking the reports, citing the message on the social networking site.

"The source for this was Ling Jihua’s office in the General Office," said a journalist close to the situation.

But the attempted cover-up spun out of Ling’s control.

Party insiders said that the police recorded the surname of the victim as Jia, which sounds like the word for "fake," a notation police officers sometimes use when the truth is being obscured. The move set off rumors connecting the dead driver to a recently retired party leader, Jia Qinglin, who was infuriated and took his grievance to Jiang, the former president.

The Central Guard Bureau, which manages leaders’ security, also was mobilized to assist in the cover-up, the insiders said. That riled the bureau’s former chief, an ally of Jiang, and the current chief, Cao Qing, who already had qualms about Ling.

"They say that Ling was always calling up Cao Qing and telling him to do this and do that," said one woman from an official family. "Ling was excessive and disrespectful."

The issue came to a head in July as the leadership debated Bo’s fate and hashed out plans for the leadership transition.

"Just as they were discussing the arrangements, the old comrades raised this," said an official from a central government media organization. "They said that leaders have to obey party discipline, so this person was not qualified to be promoted to the Politburo."

In one exchange with Hu, Jiang also questioned Ling’s "humanity" over accusations that he maintained his busy schedule and did not properly observe his son’s death, several people said.

Hu felt compelled to sacrifice his ally, partly because the party was also pursuing the case against Bo on disciplinary grounds.

"Hu didn’t want to give the others something they could use," said a relative of a former leader.

In a pivotal shake-up, Ling’s designated replacement, an old colleague of Xi’s, arrived in July, six weeks before the reshuffle was publicized.

By September, party insiders said, Hu was so strained by the Ling affair and the leadership negotiations that he seemed resigned to losing power and influence. Meanwhile, Xi began taking charge of military affairs, including a group coordinating China’s response to the escalating row with Japan over disputed islands.