Having been a People's Action Party MP for 16 years, Madam Halimah Yacob is aware there are those who question her ability to be non-partisan if she is elected president.
"I know people have that concern because of my past affiliation with the PAP," she told The Straits Times in an interview.
"But I just want to say that the president has a duty first and foremost to Singapore and Singaporeans, and not to any party."
She also has the track record to prove her independence, noting that whether as a unionist or parliamentarian, she had not always toed the government line.
An occasion she remembers clearly was when she abstained from voting on amendments to the Human Organ Transplant Act in Parliament in 2007. Changes tabled by then Health Minister Khaw Boon Wan would allow organ recipients to reimburse donors' expenses if they wished.
She was concerned that this would lead to poor people being persuaded to "sell" their organs. The party Whip was lifted, and she abstained, sending a strong signal of her misgivings. She recalled: "I decided not to say yes. I didn't ask the Health Minister how he felt, but I can still remember the expression on his face."
She noted that former president Ong Teng Cheong was a PAP politician-turned-president, but few would describe him as "a president that really only toed the line of the Government". A public disagreement surfaced between Mr Ong and the Government in 1994, when he questioned a proposed amendment to his powers without his consent. He asked for a court ruling on the matter, and in 1995, a special tribunal of High Court judges backed the Government.
"So, it is not so much a question about your affiliation, but it is a question of how you exercise the responsibilities given to you."
If elected, Madam Halimah said, she hopes to set the tone for society. The president may not have executive powers, but can help shape society through initiatives or speeches, she said.
Under the Constitution, the president has powers to veto appointments to key public service posts and is a custodian of the reserves and a unifying symbol.
"It is not a role where I can say, 'I allocate resources to education'. I won't have that power. I can't make policies, I can't make laws," she said. "One role is not often articulated - the president can set the tone for society as a whole, and I want to build a society that is progressive, inclusive, caring and compassionate."
She cited how former presidents played that role well.
President Yusof Ishak, through his speeches and behaviour, set the tone of multiracialism during the early years of nation-building, when race relations were fractious, she said.
President S R Nathan, who set up the President's Challenge, galvanised people to come together to raise funds for charity, she added, noting President Tony Tan Keng Yam continued this.
"That is the kind of tone that can be set by the president, regardless of whether you have power to make policies."