Some political analysts are sensing the emergence of localism as a new force in the political landscape of Hong Kong that has traditionally had only two blocs since the 1997 handover.

While votes were still being counted at press time, few believed Leung had what it took to win a Legislative Council seat this time.

That, however, was never his endgame.

Leung is playing for the long term. Indeed, observers say the rising tide of localism is a factor other parties can no longer afford to shrug off and not take into account in their election arithmetic in future elections.

Sunday’s by-election was triggered by the resignation of former Civic Party legislator Ronny Tong ka-wah. Tong, regarded as a moderate pan-democrat, quit the party last summer after a split with party colleagues over the way to fight for one-man-one-vote in Hong Kong. He also quit the legislature.

Back then, all talk of a by-election was pitched as a straight fight between the two traditional rival pan-democrat and pro-Beijing blocs. But the localist camp caught much public attention after the February 8 Mong Kok riot. Leung was allegedly involved in the riot and faces a rioting charge.

Whoever emerges as the winner of the by-election will be a seat-warmer because the current term of the Legislative Council ends in July. A general election is expected in September.

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The results of the vote may be the canary in the coalmine for Hong Kong’s deeply riven political scene. If the votes within the two traditional camps become even more split because of internal competition, then the September polls could spell even more trouble for the established parties.

The votes Leung could collect will also be a test of whether the momentum from the spectacular gains young activists made in last year’s district council elections could be sustained.

“The Lee Po saga and Beijing’s strong rhetoric against the Mong Kok rioters have partly made Leung a hero,” said Dr Chung Kim-wah, a political observer at the Polytechnic University. He was referring to the mysterious disappearance of bookseller Lee Po who somehow managed to resurface on the mainland without proper travel documents amid speculation that he had been abducted by mainland law enforcers in Hong Kong.

“Public insecurity has partly fuelled the rise of Leung and some people may turn to radical localism because they are becoming convinced that status quo politics cannot get Hong Kong anywhere.

“He might not win this time. But the campaign is gaining momentum. Under the current election method, if a localist candidate can get as little as 10 per cent or even less of the vote in a general election, he or she can land a seat in the legislature.”

This is possible through the highly intricate proportional representation system introduced after the 1997 handover.

Chung cited the results of the 2012 election in which Gary Fan Kwok-wai of the NeoDemocrats was able to win a seat in New Territories East by collecting slightly more than 6 per cent of votes in the geographical constituency.

Leung, who was half an hour late for his election rally to greet supporters in Tseung Kwan O, said yesterday: “Just about a month ago, I was rallying by myself. Today I have around 500 volunteers helping me.”

He conceded he lacked experience in politics but saw it as an advantage. “I am not a politician. I say and do what I believe in.”

His rapid rise has also partly accounted for the lacklustre appeal of the so-called moderate or middle-of-the-road candidates, who aim at pushing for improvements through dialogue with the establishment.

Various pre-election opinion polls showed Alvin Yeung Ngok-kiu of the opposition Civic Party and Holden Chow Ho-ding of the pro-Beijing Democratic Alliance for the Betterment and Progress of Hong Kong were in front.

Yeung’s lead was however less clear-cut after the Mong Kok riot. Localist supporters see Yeung as not radical enough to effect change, while critics have vented their anger at the barrister for offering legal assistance to the alleged rioters.

Chung believed the localist factor would dilute traditional pan-democrat votes.

While in some pre-election opinion polls Leung came in third place, others showed he was neck-and-neck with Nelson Wong Sing-chi of the middle-of-the-road Third Side party.

“The chaos in the legislature in the past few days showed clearly that a council that is dominated by two rival camps will not be able to achieve anything. I think there is a need for a third voice in the council,” said Wong, referring to Saturday’s Finance Committee meeting which degenerated into a farce as pan-democrats leapt forward to bar the pro-government committee chairman from taking his seat to preside over the meeting in a bid to derail the government funding request for the high-speed rail link from Hong Kong to Guangzhou.

Ronny Tong spoke of Wong’s campaign: “That Mr Wong did not seem to make much impact does not mean the moderate third road has failed. Everyone can claim he or she is pursuing a third road. But whether he or she really knows what it is is another thing.”

Political scientist Dr Cheung Chor-yung of City University agreed that Wong had been too weak in getting his message across about the “third road”. “The Mong Kok riot has also stolen much of the media spotlight from the so-called third road in favour of localism,” said Cheung.

Some voters did not buy Wong’s ideas either. While they were unhappy with the recent filibustering by pan-democrats in the Legislative Council, they claimed they would vote for the pro-establishment candidate Holden Chow, instead of Wong.

In Sha Tin, Wilson Chan, a logistics worker who said he had voted for Chow, said: “I just don’t want to vote for those who keep making a scene.”

Another, auditor Eddie Ng, said: “The pan-democrats keep filibustering and it is inevitable that it will take a toll on social welfare.”

In the 2012 general election, Wong, who was then a Democrat, won 21,118 votes, or roughly 4.5 per cent of the total.

By Monday morning, the winner of the by-election will have been crowned and will be making the rounds to thank voters. The two traditional camps’ election committees will later conduct a post-mortem on who took votes away from them – one of their own or the new political player from the localist camp.