The Sarawak-based seat fell vacant after the death of its incumbent member, Robert Lau Hoi Chew, from liver cancer on 9 April 2010.

In the previous general election in 2008, the incumbent, Hoi Chew retained the seat with a 3,235-vote majority against Wong Ho Leng, and Lim Chin Chuang of the People's Justice Party.

[3] In this election, known as the "Battle of the Mighty Rejang", the government and opposition went head-to-head on a number of local issues concerning Sarawak, including poverty, education and development.

[7] Within a few days, the Sibu branch of SUPP recommended Robert Lau Hui Yew to contest the by-election for the governing Barisan Nasional coalition.

Hui Yew was the second cousin of Hoi Chew and the son of Lau Swee Nguong, chairman of the KTS Group of companies.

[10] Opposition Leader and People's Justice Party (PKR) adviser Datuk Seri Anwar Ibrahim scheduled a visit to Sibu on 18 April.

[12] The Deputy Prime Minister of Malaysia, Tan Sri Muhyiddin Yassin visited Sibu on 19 April, expressing confidence that the voters were leaning towards supporting Barisan Nasional.

[19] The by-election was widely known as the "Battle of the Mighty Rejang"[20] and was seen as a litmus test for the popularity of the opposition Pakatan Rakyat and governing Barisan Nasional coalitions on a[clarification needed] including land rights, poverty, native displacement and unemployment in Sarawak.

[22] The Barisan Nasional did not initially release a policy manifesto for the by-election,[23] but sought support on the basis of its claim to have caused Sibu's economic growth and development.

[24] Nevertheless, late in the campaign, the BN-SUPP candidate, Robert Lau Hui Yew, himself released a manifesto in which, according to Bernama, he mentioned that he would prioritise "getting more investment, job creation, skills training for single parents to increase their income, install more CCTVs in town to improve security and reduce street crimes rates as well as to transform Sibu into a 'wireless' township.

[26] Besides that, some 246 families living in an under-developed region in Sungai Igan within the constituency had received a total of RM147,600 as a one-off allocation from the Federal Government.

[27] Four Methodist churches in town had been given special grants totalling RM1.75 million from the BN federal government in the final hours of the by-election campaign.

[30] The SUPP also claimed that if the DAP was to be voted in kampua noodles could no longer be sold as they were mixed with pork lard; a reference to PAS's policy to establish Malaysia as an Islamic state.

[31] Abdul Taib Mahmud, the BN chief minister of Sarawak, revised new land renewal rates which took effect on June 1.

[32] Najib Tun Razak, the Prime Minister and leader of BN, promised voters in Rejang Park, a DAP stronghold, 5 million ringgit to alleviate floods if SUPP's Robert Lau Hui Yew won the seat,[33] stating at an election appearance: "Do we have a deal or not?

[43] The announcement of the result was marred by a two-hour-long delay because of arguments over the discrepancies of the postal votes by Pakatan Rakyat election agents.

[49] Lim Kit Siang of the DAP mentioned that the party's win in Sibu renews Pakatan Rakyat's Putrajaya dream,[50] referring to PR's ambition to form the Federal government in the next 13th general election.

[53] Abang Johari Openg, Sarawak state Minister for Housing and Urban Development, blamed the "provocative tactics" allegedly employed by Pakatan Rakyat leaders for causing the defeat of the SUPP candidate, referring to the raising of the 'Allah' issue.

[55] As for the SUPP, its president George Chan Hong Nam who congratulated its winning candidate Wong immediately after the election result was announced, said that his party was completely overwhelmed by DAP's streetfighter style of politics[56] and said, "these outsiders with their street culture have come to spoil the good nature of Sarawakians," and that "SUPP would do all it could to ensure that the "outsiders" do not gain a foothold here".

[58] Ibrahim Ali, the president of Malay rights group Perkasa labelled the Chinese in Sibu as ungrateful for not voting for the BN.

[60] Nevertheless, the losing candidate, Lau Hui Yew, pledged that he will continue to serve the people as a councilor of Sibu Municipal Council (SMC) and as a party leader.