Despite this however, Lam is firm favorite to win Sunday's contest. Because in Hong Kong -- despite the polls, the public debates, and the political advertising littering the streets -- most people don't get a vote.

Only 1,194 people -- 0.01% of the population -- on a "broadly representative" election committee get to choose who becomes the city's next leader.

Scrapping the committee -- which is dominated by pro-Beijing interests and toes the Party line -- was a key demand of the "Umbrella Movement" pro-democracy protests which shut down parts of the city for months in 2014.

Joshua Wong, one of the leaders of the 2014 protests, told CNN the "most important thing for us in the short term" is to fight for the right to vote for the next Chief Executive.

Finish line

In a televised debate last week, Lam acknowledged the importance of public opinion.

"I trust Hong Kong people 100%. So when the mainstream opinion is different from mine, I will definitely accept Hong Kong people's opinion," she said.

"If public opinion renders me unsuitable to serve as chief executive, I will resign."

Lam -- CNN has requested an interview -- knows from experience the difficulties of governing a city that has turned against its leader.

That lack of widespread support even among the elite hurt Leung, who faced repeated mass protests throughout his tenure, said Duncan Innes-Ker, Asia regional director for the Economist Intelligence Unit.

"Some Beijing officials appear to feel that the relatively narrow margin of victory that Leung secured served to undermine his legitimacy," he said.

That may dash Tsang's hopes of a surprise win, as Beijing will want to ensure Leung's successor has the clear support of the commission, Innes-Ker said.

"John Tsang's tactic positioning himself as the popular choice has echoes of the 2012 race," he added. "(But) Carrie Lam has not faced any scandals of similar impact."

Not that Lam has been gaffe-free. One of her last actions as deputy leader was to approve a controversial Hong Kong version of the Palace Museum, in Beijing's ancient Forbidden City.

The plan was announced without public consultation, and critics quickly seized on a giant advert for the museum -- which depicted the gates of the Forbidden City in front of Tiananmen Square -- to stage protests calling for justice for the Tiananmen massacre of 4 June 1989.

Lam did not respond to a request for comment about her popularity with the public.

Popular vote

While Tsang -- a lifelong bureaucrat who has met with senior Chinese leaders including President Xi Jinping -- is hardly an anti-establishment choice, he has attracted support from pro-democracy legislators and called for the way Hong Kong's leader is chosen to be reformed.

"I think for Hong Kong to choose a chief executive that the general population would have trust in, would support, I think that is a very important step," he told CNN.

"We all want to have universal suffrage ... and this is also something important for the next chief executive because someone who is voted in by the general population would have mandate that a small circle election would not provide."

Lam did not respond to a request for comment about future political reform.

Whoever Hong Kong's next Chief Executive is, he or she is likely to get an early taste of 2014's "Umbrella Movement."

"The fight isn't over," Wong said. "We're ready to get back the chance to vote in the election. Don't just implement selection, we need election."