By Chris Hogg
BBC, Hong Kong
Hong Kong's acting chief executive has stepped down to start campaigning for the permanent job as leader.
Mr Tsang wants the poll to give him a strong mandate
Donald Tsang resigned shortly after lawmakers passed a controversial amendment cutting the next leader's term from five years to two.
It was the last step in a legal battle which saw Beijing step in to adjudicate on the matter.
The dispute began in March when Hong Kong's former leader Tung Chee-hwa resigned, citing failing health.
Mr Tsang lost no time in clearing the decks ready to start his campaign.
Under Hong Kong law he had to stand down from his job as acting chief executive in order to join the race for the permanent post.
Question of trust
There is no doubt that he will win, but he is reported to have already set up a campaign team and engaged two public relations firms to help him secure as many votes as possible from the 800-strong election commission.
Mr Tsang, a colonial civil servant when the British ruled Hong Kong, had refused to announce formally his intention to run until the question of the term of office was resolved.
The issue of how long the new chief executive should serve has been controversial and subject to legal challenges by lawmakers and others.
Many people resent the interference of Beijing in an issue they argue should have been left to Hong Kong to decide.
The Chinese leadership supports Mr Tsang, but they do not yet trust him, analysts say.
He is likely to face competition from two other lawmakers, but only if they can secure enough nominations to join the race.