The choice made by 40 percent fence-sitters can spring a surprise for the three political parties contesting in the Sungai Besar by-election on June 18.

Political analyst from Universiti Kebangsaan Malaysia, Assoc Prof Datuk Samsu Adabi Mamat said the fence-sitters' decision would be one of the interesting elements in the by-election, as their votes were seen as an "incentive" for the contesting parties, particularly PAS after it left the opposition pact, Pakatan Rakyat.

"Previously, they were mainly PAS and Pakatan Rakyat supporters. However, after PAS quit Pakatan Rakyat, the fence-sitters may be divided in voting for which side as their party had split.

"Perhaps they will now favour Amanah or BN (Barisan Nasional) or not vote at all. We don't know as anything can happen without us expecting it," he told Bernama.

The Sungai Besar parliamentary seat by-election will see a three-cornered fight involving BN, PAS and its breakaway group, Parti Amanah Negara (Amanah), following the death of the incumbent MP Tan Sri Noriah Kasnon, who was also Plantation Industries and Commodities Deputy Minister, in a helicopter crash in Sebuyau, Sarawak on May 5.

In the 13th general election (GE13), Noriah defeated PAS candidate Mohamed Salleh M Hussin with a 399-vote majority.

Samsu Adabi who is an expert on Islamic politics and Muslim minorities, said in the GE13, 30 percent of the votes went each to BN and Pakatan Rakyat, while 40 percent of the voters were fence-sitters.

"In this by-election, however, the 30 per cent votes for Pakatan Rakyat will be split into half after PAS quit the pact. Perhaps 20 per cent will now go to Amanah which is representing Pakatan Harapan and only 10 percent to PAS, or maybe it's the other way round. But the number of fence-sitters remains the same.

"Budiman will spring a surprise as he has no problems with the UMNO grassroots and he is also popular with the Chinese community in Sungai Besar," he said.

Barisan Nasional is fielding Budiman Mohd Zohdi, the Sungai Panjang assemblyman, to defend the Sungai Besar seat.

"Walkabouts, ceramah sessions and visits to the homes of the needy can help draw support from voters, especially the Chinese. Any possible surprise cannot be underestimated as PAS and Amanah may also spring a surprise," said Samsu Adabi.

Geostrategist Prof Dr Azmi Hassan from Universiti Teknologi Malaysia said: "BN can win in this by-election as Budiman is a local, who the residents of Sungai Besar find approachable and friendly, which is a bonus to his party."

Azmi is optimistic that BN will be able to increase its majority votes this time, while he expects Amanah candidate Azhar Abdul Shukur to have difficulty capturing the seat compared to his two challengers, Budiman and Dr Abdul Rani Osman from PAS.

He said the two (Budiman and Abdul Rani) had better credentials in terms of profile and reputation as they were no strangers in Selangor, while the Amanah candidate held no political position and his political involvement had not been conspicuous.