The tycoon's son was widely considered a shoo-in as Hong Kong's next leader, with key backing from Beijing. Then came the scandals, including an extramarital affair and an uproar over his illegally built underground leisure palace.
Then followed Henry Tang's evasive answers to questions about long-standing rumors of an illegitimate child, which Hong Kong's press took as tacit confirmation.
The gaffes torpedoed Tang's popularity, and Chinese leaders are now keeping their distance. But he has rejected calls to drop out of the race for the March 25 selection, and has taken to sniping at his main rival, Leung Chun-ying, who's grappling with a scandal of his own over a possible conflict of interest involving his property firm.
Hong Kong has never seen anything quite like this year's boisterous campaign.
Not in the more than 150 years when Britain was in charge and London dispatched the governor. Not since 1997, when China regained control and continued cozy arrangements of power while promising eventual democracy in the freewheeling, semiautonomous territory. In the meantime, it formed a committee of local business leaders and other elites, most of them loyal to China's communist leaders, to select the chief executive.
But this year's leadership race has defied Beijing's penchant for control while highlighting the fear among many Hong Kongers that Chinese rule may be eroding virtues that define their city, including the rule of law and clean governance, while keeping true democracy far away on the horizon.
"People are angered by all these scandals and angered by the fact that they have no choice," said Lee Cheuk-yan, a pro-democracy lawmaker.
Alan Leong, another pro-democracy legislator who ran against the city's current leader in 2007 even though he had no chance, said the election process amounts to a fight among "factions of the Chinese Communist Party and different interest groups in the Hong Kong power echelons."
One of Asia's richest cities, Hong Kong is a major financial hub and home to the Asian headquarters of multinational companies. Its 7.1 million residents include an educated middle class. Its bureaucracy and courts were long considered corruption-free.
Beijing promised to preserve the freedoms of press and speech and other Western-style rights not seen on the mainland, and it pledged in 2007 that Hong Kong could elect its own leader in 2017 and all of its legislators by 2020 at the earliest.
But Beijing has not laid out a roadmap, raising fears it many backtrack on those promises or continue to pull strings behind the scenes. Closer economic integration with China, a local government that seems beholden to Beijing and a growing rich-poor gap have left the middle class worried that Chinese rule and close ties to local tycoons are risking the city's future.
They also fear that it is importing a culture of corruption from the mainland.
The current Chief Executive Donald Tsang also has been hit by an unprecedented investigation after reports he accepted a private jet and yacht trips to Japan, Thailand and Macau and other favors from rich business pals.
Tsang apologized and said he followed the rules and repaid his hosts for the trips. He also gave up a posh apartment intended for his retirement that news reports said was owned by a mainland Chinese property magnate.
Still, thousands of protesters took to the streets to vent their frustrations over the allegations. They waved banners and chanted slogans calling for Tsang to step down.
"It's a shame that Hong Kong has become one of the corrupted cities in China," said Lee, the pro-democracy lawmaker, who took part in Saturday's march. He said public anger would grow unless Hong Kong gets full democracy. "There will be protest after protest. Because the credibility of the government is so low."
China's rulers have been obsessed with maintaining control in Hong Kong since half a million people took to the streets in 2003 to protest anti-subversion legislation, taking Beijing by surprise.
Hong Kongers frequently air their grievances in the streets. In January, demonstrators rallied in front of the Chinese central government's liaison office after a Beijing scholar compared the city's residents to dogs. Some brought along their pet dogs to express their anger.
Tang, initially believed to be Beijing's preferred choice to succeed Tsang, is another big target.
He admitted an extramarital affair, and then his popularity sank further following revelations of an illegally built 2,250-square foot (209-square meter) basement that reports said was outfitted with a Japanese spa, home theater, wine cellar and wine tasting room. In a city where most people live in tiny apartments and the government has been trying to crack down on illegal structures, it sparked outrage over double standards.
Polls show his approval rating has fallen to about 19 percent. But the heir to a textile fortune has the backing of tycoons including Li Ka-shing, the city's richest man.
Leung, the son of a police officer, is popular with the public. Polls show he has the support of more than 50 percent of the population. That's despite allegations that when he was a judge on a decade-old design competition for an arts center, one of the contestants was linked to his own property firm. Lawmakers have voted to investigate.
This year's mudslinging and muckraking have created a dilemma for China's communist leaders.
Tang's scandals are making them think twice about their initial support because they don't want him undermined by public doubt from the start, said Dixon Sing, an associate professor of political science at Hong Kong University of Science and Technology.
Leung, however, is making the tycoons apprehensive because he's seen as more willing to carry out large-scale social policy reforms that could undermine their business interests, Sing said.
For example, Leung wants to boost public housing supply in land-scarce Hong Kong, which would upset the billionaires who have built property development empires.
Beijing has delivered no clear public signals on which way it's now leaning. Vice President Xi Jinping, who's expected to be named China's next president later this year, gave no hint when he met the two candidates at a recent high-level meeting in Beijing.
As the March 25 selection date looms, Beijing faces a tough choice: choose one and risk upsetting the tycoons, choose the other and risk an explosion of public anger.
Henry Tang's campaign website: http://www.wearetomorrow.hk
Leung Chun-ying campaign website: http://www.cyleung2012.com/
Follow Kelvin Chan at twitter.com/chanman