A small electoral college will choose a new Hong Kong leader amid accusations of meddling by Beijing, denying the Chinese-ruled financial hub a more populist leader perhaps better suited to defuse the political tension.
The vast majority of the city's 7.3 million people have no say in their next leader, with the winner to be chosen by a 1200-person "election committee" stacked with pro-Beijing and pro-establishment loyalists.
Three candidates are running for the top post, two former officials, Carrie Lam and John Tsang, and a retired judge, Woo Kwok-hing. Lam is considered the favourite.
"I hope we all remember on March 24 2017, we Hong Kong people have all come together and given our most sincere blessings for a more united, a better Hong Kong," Tsang told a rally of thousands of cheering supporters on Friday night.
Several hundred protesters marched on Saturday denouncing Beijing's "interference" in the election amid widespread reports of lobbying of the 1200 voters to back Lam, rather than the more populist and conciliatory former finance chief, Tsang.
Security was tight on Sunday around the harbourfront voting centre with 2000 or so police officers expected to be deployed in the vicinity in case of unrest.
Since Hong Kong returned to Chinese rule in 1997, Beijing has gradually increased control over the territory even though China had promised wide-ranging freedoms and autonomy under the formula of "one country, two systems", along with an undated promise of universal suffrage.
Many fear that Lam will continue the tough policies of staunchly pro-Beijing incumbent Leung Chun-ying, a divisive figure who ordered the firing of tear gas on pro-democracy protesters in 2014 and who wasn't seen to be defending Hong Kong's autonomy and core values.
The political upheavals with Beijing over the city's autonomy and democratic reforms -- that many hoped would have allowed a direct election this time round - have roiled a new generation and weighed on the city's economy, ranked 33rd globally by the World Bank in 2015.
Political and social divisions, mainly over democracy and anxieties over China's creeping influence, have dominated political debate leading to some legislative and policy-making paralysis and the stalling of major projects, including a cultural hub and high-speed rail link to China.