The two-time Oscar winner commented in a recent interview that he became totally fascinated with Lincoln, a man who was at the centre of a historical crossroads in the US.
"It's the man himself that invites you, because he was so open. That was one of the most beautiful surprises of getting to know him, finding how insanely accessible that man was," Flicks and Bits quotes him as saying.
He continued: "At the time it was very dangerous, in his case, to be accessible. But the White House was an ever open door, people could come and go. It was bedlam in there. But he was accessible – some parts of him were. So that became an opening in a way I think. One almost felt welcomed.
"He put me at my ease, strangely. Having first made me very uneasy, it was learning about him that put me at my ease. It gave me the thought of, 'Maybe I could try to do this'."
Day-Lewis went on to praise Lincoln screenwriter Tony Kushner, who adapted the film from Doris Kearns Goodwin's book Team of Rivals.
"In such a rich way had Tony Kushner's script already suggested the man through his intellect, through his humour, through his melancholy – both domestically and in public office," he explained.
"The contrast between those two things, that's something like food and drink to me, seeing somebody who's life is lived at one and the same time in that strange paradox of public and private."
Lincoln star Joseph Gordon-Levitt previously joked that the film's set practically "revolved around" Day-Lewis.
The film – which also stars Tommy Lee Jones, Sally Field and Jared Harris - is released on November 16 in the US and January 25 in the UK. Watch a trailer below: