Hong Kongs finance chief resigned on Monday ahead of what is widely expected to be a tilt at the city leadership.
John Tsang -- nicknamed "Mr Pringles" by local media for his resemblance to the crisp brand's mascot -- is seen as a more moderate alternative to current leader Leung Chun-ying, who said on Friday he would step down in July.
The city has become sharply divided under Leung, whose term has been marked by anti-Beijing protests. Opponents cast him as a puppet of the Chinese government squeezing the semi-autonomous city's freedoms.
The finance secretary has yet to confirm whether he will run for the leadership but his resignation is seen as a signal that he will enter the race. Candidates are not allowed to hold a government office if they want to stand for chief executive.
Although Tsang has a better public image than Leung, he is still an establishment figure.
Pro-democracy campaigners have warned the next city leader will simply be another Beijing yes-man as the vote system is skewed.
The chief executive is chosen by an electoral committee made up of representatives of special interest groups, weighted towards Beijing.
Mass rallies in 2014 called for fully free leadership elections, but failed to win concessions on reform.
Special interest groups voted for members of the election committee Sunday -- final votes are still being counted but of almost 1,200 only around a quarter are likely to come from the pro-democracy camp.
Speculation that Tsang would run for office intensified last year after China's President Xi Jinping shook his hand during a meeting in Beijing.
There was another handshake between the two in September at the G20 in Hangzhou.
Both were taken as signals that China was endorsing Tsang's candidacy for the leadership.
Former security minister and current senior lawmaker Regina Ip is also expected to announce her candidacy this week.
Ip is hated by the pro-democracy camp for supporting controversial anti-subversion law Article 23 when she was minister in 2003. It was dropped after hundreds of thousands of residents protested.
However, she has a strong support group in the establishment camp -- in recent legislative elections Ip was one of the most popular candidates receiving 60,000 votes.
Only one candidate has declared they are running for the leadership so far -- retired judge Woo Kwok-hing who has said he wants to help Hong Kong overcome its divisions.