In 2001, the NSP became a founding member of the Singapore Democratic Alliance (SDA), along with the Singapore Justice Party (SJP), the Singapore People's Party (SPP) and the Singapore Malay National Organization (PKMS).
At the 2001 general election, Chiam was re-elected as MP for Potong Pasir, and NSP Secretary-General Steve Chia became the SDA's second representative in Parliament when he earned a position as a Non-Constituency MP.