Opposition veteran Wong Wee Nam, who contested the 1997 General Election, died on Saturday after battling Parkinson's disease for several years.
He was 72.
Dr Wong was a prominent advocate and observer of Singapore's opposition politics, and had close ties to the Singapore Democratic Party (SDP). He, however, contested the 1997 election under the National Solidarity Party (NSP) banner.
Among those who paid tribute to the retired general practitioner were the SDP and its chairman Paul Tambyah, Singapore First Party secretary-general Tan Jee Say as well as former patients.
The SDP said on its Facebook page that Dr Wong was a mentor to many of its younger members, disclosing that he nearly stood as an SDP candidate in the 2011 General Election, but withdrew at the last minute for familial reasons. Still, Dr Wong was "in the thick of our campaign, always a source of strength for his party colleagues", the party said.
In 1997, Dr Wong was part of a five-man NSP team that went up against the People's Action Party in Hong Kah GRC, and garnered 31 per cent of votes.
The SDP said his views influenced many of the ideas in the party's policy papers, especially on healthcare. On his Facebook page, Dr Tambyah said of Dr Wong: "A kind doctor, deep thinker, Singaporean patriot and good friend. You will be missed."
The Singapore People's Party also called Dr Wong a "highly respected doctor and leader", adding that he was a friend of its leader Chiam See Tong.
Meanwhile, Mr Tan credited Dr Wong for pushing him into politics. They had met through a mutual friend, he said in a Facebook post.
"Wee Nam persuaded and encouraged me to join SDP and introduced me to Dr Chee Soon Juan... He provided good advice and guidance along the way, always putting the interests of Singaporeans at the heart of his advice," he wrote. Dr Chee is the current SDP secretary-general.
Dr Wong also contributed articles to socio-political websites and The Straits Times Forum page.
He graduated in 1972 from the then University of Singapore. After national service, he went into private practice as a GP until his retirement in 2016, said the Singapore Medical Association News.
Mr Simon Lim, 60, whose home in the 1970s was in Clementi where Dr Wong had his clinic, remembers the doctor going to his flat to treat his late grandmother, who was too weak to walk to the clinic.
"We were poor then and could pay him only what we had, but he did not mind," Mr Lim, who works in an engineering firm, told The Straits Times. "I am forever grateful to him."
Dr Wong is survived by his wife and two daughters.