His announcement came against the backdrop of a split within the pan-democrat camp, which holds one-third of the seats in the 1,194-member Election Committee – the body that will elect the next leader in March.

He worried the pro-democracy bloc would lose their say and moral high ground if Tsang put forward bad policies during his term, if elected.

Leung’s surprise announcement received the cold shoulder from his traditional pan-democrat colleagues, with only four localist lawmakers – Eddie Chu Hoi-dick, Raymond Chan Chi-chuen, Lau Siu-lai and Nathan Law Kwun-chung – attending the press conference.

The veteran activist from the League of Social Democrats was also hit with criticisms on his own Facebook page.

Supporters questioned why he would give up on his long-held principles for something that is unlikely to succeed and even contribute to the victory to Carrie Lam Cheng Yuet-ngor, the former Chief Secretary who is perceived as Beijing’s favoured candidate.

Fellow pan-democrats cast doubt over Leung’s candidacy, believing it would not tilt the scales in their favour, especially as Hongkongers wanted to maximise the value of their votes in this very election.

“Frankly, I don’t feel worried about endorsing Tsang,” a pan-democrat, who wished to stay ­anonymous, told the Post. “Public opinion is so obvious, how could anyone turn a blind eye to it?”

As of 6pm yesterday, 57 per cent of the 8,748 Hongkongers who cast a vote via the electronic platform backed Tsang – more than double the 2,083 votes for Leung. But the pan-democrat also agreed they would need someone from the camp to take the lead in endorsing Tsang so others could comfortably follow, especially after the contender pledged to revive the contentious national security legislation.

Each aspirant needs 150 nominations before being recognised as a formal candidate. Lawmaker Wong Kwok-kin, of the Federation of Trade Unions, estimated Tsang could bag 50 votes from the Beijing-friendly bloc, meaning he would need at least 100 more from pan-democrats. Leung’s bid is expected to hit ­retired judge Woo Kwok-hing, another relatively liberal contender who is fully counting on pan-democrats’ support, the hardest.

Political scientist Dr Chung Kim-wah, of the Polytechnic University, said Leung’s bid would widen the rift within the pro-democracy bloc.

“It would now be more embarrassing for pan-democratic voters to nominate Tsang or Woo after the participation of Leung, who shared the same political stance with the camp,” he said. Leung admitted he was “not the best person to run”, noting he had lobbied Civic Party’s Audrey Eu Yuet-mee to contest, but failed. He also ­dismissed claims that he would split the votes for Tsang.

“I cannot force the electors to vote for me, so how can I split the votes?” he asked. “Don’t blame the candidate.”

The 326-strong alliance of the pan-democrats voting in the ­Election Committee, are expected to meet Saturday to discuss strategy in the lead up to the election.