Over two years, Sin stood as the pro-tem leader until Chiam joined the party and assumed leadership in December 1996, at the time the Parliament was dissolved ahead of the 1997 general election.

Though Chiam was the only SDA member to win an elected seat in Parliament, he was joined in Parliament by SDA member Steve Chia (then-leader of the National Solidarity Party) who became a non-constituency MP after securing 34.6% of the votes in the constituency of Chua Chu Kang, which was the highest percentage of the vote secured by a losing opposition candidate at the election.

Though Chia increased his share of the vote in Chua Chu Kang to 39.63%, this was lower than the 43.9% gained by the Workers' Party in Aljunied GRC.

He reportedly accepted the conditions the RRP set out for joining the alliance, but the terms of entry were opposed by other members of the Central Executive Committee (CEC) who blocked the move.

This was Loh's debut in politics, although she had tirelessly campaigned with her husband over the years in many general elections in Singapore, including Cairnhill and Potong Pasir constituencies.

[9] Former NSP member Jeannette Chong-Aruldoss joined the party prior, and contested Mountbatten SMC just as Chong did in the 2011 elections.

[10] In January 2018, it was reported that Jose Raymond, a former Press Secretary to Vivian Balakrishnan (who also served as Chief Executive of the Singapore Environment Council and current Minister of Foreign Affairs), had joined the SPP.

Also in the same year, WP's Low Thia Khiang surpassed Chiam as the longest-serving opposition MP, having served in Parliament since 1991.

On 22 December 2020, SPP Chairman Jose Raymond announced that he was retiring from politics, while revealing that the Assistant Secretary-General, Ariffin Sha, resigned from the party in August.