The Electoral Boundaries Review Committee report, released on 24 February 2011 after having been placed with the Prime Minister's Office three days earlier, upped the number of SMCs from nine to 12 for the first time in three GEs. The average size of GRCs would be reduced five members, paving way for the return of four-member GRCs that was last seen in the 1997 GE. Also, a one-day cooling-off period before polling day was introduced, extending the difference between the nomination and polling days to at least ten days, up from the minimum nine.

Two seats, one within Jurong GRC and the other within Ang Mo Kio GRC, had become vacant after the death of PAP MPs Ong Chit Chung in 2008 and S. Balaji in 2010 respectively. However, the PAP government was not obligated by the law to hold by-elections and did not do so despite calls by several opposition parties, NMPs and activists.

For the second time, PM Lee Hsien Loong was leading PAP into a GE and the most hotly contested one since 1963. With its campaign theme "Securing Our Future Together", the ruling party was fraught with several challenges such as rising costs, a widening income gap, inadequate housing supply, a large influx of foreigners, financial losses incurred by national corporations and several prominent security lapses. The decision to field Tin Pei Ling, an inexperienced candidate who had committed a few gaffes, also created some controversy.

As a result, PAP saw a GRC, traditionally regarded as its "fortress", fall for the first time. The popular George Yeo, new candidate Ong Ye Kung who is son of former Barisan lawmaker Ong Lian Teng and sole woman minister Lim Hwee Hua were among the casualties. The last was a deja vu of 1991 where first woman minister Seet Ai Mee lost her seat. Tin became the youngest MP since 1966 but the team led by Senior Minister Goh Chok Tong, which she was part of, fared below expectations.

Compared to the previous GE, the opposition camp was more fragmented this time. Additional entrants to the fray were NSP and SPP, both which had left the SDA alliance and reverted to their own banners for the first time since 1997, as well as the newly formed RP.

Despite so, its position had strengthened and fielded several high-profile recruits including renowned international lawyer Chen Show Mao who was standing under WP ticket and SM Goh's former principal private secretary Tan Jee Say who was with SDP. Collectively, the opposition contested nearly seat except for a failed bid in Tanjong Pagar GRC helmed by Minister Mentor Lee Kuan Yew, which could have been the first independent GRC team comprising mostly renegade PKMS and SF members.

Opposition veteran J. B. Jeyaretnam passed away shortly after establishing RP in 2008, leaving it rudderless until his elder son, Kenneth Jeyaretnam took over. He ousted his late father's long-time loyalists, some whom formed SF. RP grew to become possibly the largest opposition party but a spate of resignations before the GE reduced its numbers once again.

Among those who left RP, several joined NSP. One of them, Nicole Seah, attracted attention with her passionate speeches and by contesting SM Goh's ward, was compared to Tin. She was also the youngest candidate in the GE. Ang Mo Kio GRC nearly became a no-contest until RP borrowed candidates from SPP.

The biggest unprecedented moves were made by the two incumbent opposition MPs, who stepped out of their "safe" seats to contest GRCs. WP secretary-general Low Thia Khiang joined hands with chairman and NCMP Sylvia Lim to contest Aljunied GRC. Replacing him in Hougang was Yaw Shin Leong. Potong Pasir MP Chiam See Tong handed his ward of 28 years to his wife, Lina Loh, to lead a SPP team in Bishan-Toa Payoh GRC.

However, the destinies of WP and SPP went down contrasting paths. Brandishing the slogan "Towards a First World Parliament", WP broke through to win a GRC, the first time for the opposition in history, while successfully defending its incumbent seat, objectives SPP failed to achieve. During the campaign, the cannons of PAP were aimed at Chen, who had been away from Singapore for many years. As polling drew closer, PAP fired directly at the credible Low, causing further ground upset.

Since independence, this was PAP's lowest share of the votes, the largest number of seats bagged by a single opposition party and the combined opposition camp, surpassing the four in 1991, and the first time opposition candidates were elected in their maiden battle. Immediately after the GE, MM Lee and SM Goh, both whom were former prime ministers, announced their retirement from the new Cabinet, marking the end of an era. Goh was conferred the title of "Emeritus Senior Minister".