WHEN asked if Australian audiences will relate to his new film, based on the final months of US president Abraham Lincoln's life, filmmaker Steven Spielberg has a simple answer. "I never thought I'd be interested in a king that stuttered. Ever," he says, referring to British historical drama The King's Speech. "That's not my business, that's not in my geopolitical sphere of interest, and yet I was very, very compelled. I think audiences want to learn something they don't know."

Seated in New York's Ritz-Carlton hotel, in the company of arguably the world's greatest actor, Daniel Day-Lewis, and revered director Spielberg, it is frankly not easy to broach the question of whether a film penned by a Pulitzer Prize-winning writer, Tony Kushner, on the subject of perhaps the greatest US president is going to be attractive to an audience beyond the US.

In his own country, there is a kind of ubiquity about the 16th president. His likeness appears on every 1¢ piece and $5 bill, and looms nearly six metres tall, hewn from marble, in a Washington, DC memorial to which every middle-schooler in the country will make an excursion at some point. Lincoln's wit and wisdom are folded, often unsourced, into common parlance via shrewd aphorisms: "It has been my experience that folks who have no vices have very few virtues." Or: "Every man's happiness is his own responsibility." Whether people know the remainder of the Gettysburg Address, they almost certainly can recite its six opening words, "Four score and seven years ago . . .", and there have been more films made about Lincoln – beginning in 1908 – than any other American president.

Might it be a stretch, I venture nevertheless, to interest non-American audiences in what New Yorker magazine film critic David Denby has drily termed a legislative thriller, "a great movie about . . . counting votes"?

"I usually find the more detailed those stories are – even if the details in themselves are mysterious – the more I like it," Day-Lewis says, admitting he took the role partly because he knew almost nothing about Lincoln. "As a cinemagoer, I always love it when doors are thrown open into worlds that are utterly unknown to me."

His performance has already earned Day-Lewis the prized New York Film Critics Circle Award for best actor and put him in hot contention for an Academy Award (nominations will be announced on January 10).

As a brief primer, this is what is significant about Lincoln's presidency: not only was he a "backwoods lawyer", considered least likely among the candidates to become head of government in 1860, but deftly he went on to form a cabinet made up of his former rivals for the leadership. With these unlikely allies, he managed to steer a country wrenched by civil war from 1861-65, reunite the north and the south, and win successful passage through Congress for the 13th Amendment, abolishing slavery. The horse-trading and back-room deals "Honest Abe" was prepared to participate in to achieve this end form the crux of the film's drama.

"For me, he is the greatest president," says Spielberg, who believes no US head of state has been tested as Lincoln was. "The decision that Lincoln had to make to not end the war until slavery was abolished was a horrifying decision . . . That was a moment where he could have saved thousands of lives, but he knew he would never have abolished slavery in his lifetime had he ended the war first."

If audiences remain unsure about the subject matter, they might confidently wager on the pedigrees of Lincoln's collaborators. Spielberg is probably Hollywood's most successful filmmaker – and undoubtedly one of the most popular. In addition to his best director Oscars, for Schind-ler's List and Saving Private Ryan, several of his films have broken box-office records. His spectacular films range from action-packed blockbusters and science fiction to sincere, issues-based political dramas.

And Day-Lewis is notoriously selective about the parts he accepts, allowing years to pass between projects. In the past decade, he has made only five films. An actor so judicious in his choice of roles has to be some guarantee, then, of a good performance, as are a worthy script and finely crafted film.

Then there is the writing. Playwright Tony Kushner, known for deep research and historical accuracy, based his script in part on fellow Pulitzer honoree Doris Kearn Goodwin's Lincoln biography, Team of Rivals, which Spielberg optioned before it was even written. "I had imagined we would tell the entire width, length and breadth of Lincoln's presidency, as Doris had chosen to do in her brilliant book," Spielberg says. "Tony's first script was, understandably, 550 pages long . . . which was a mini-series, not a motion picture. I wasn't intending to make a mini-series."

Spielberg asked Kushner to rework the script, focusing on the last four months of Lincoln's life: the end of the civil war, the abolition of slavery and the assassination of the president. In all, the film took the better part of a decade to come to fruition, but it seems it was worth the wait. Lincoln is leading the Golden Globe nominations; often a strong indication of Academy Awards contention.

"I don't ever like to take any movie I've ever made and boil it down to one or two words – it's impossible for me to do, especially with Lincoln – but I think there is something there that all of us can relate to, and that's what makes a great leader," Spielberg says.

Day-Lewis inhabits his role uncannily. Although this ability to transform is an alchemy we have seen the actor perform many times – from a disabled writer to a native American to a ruthless oil prospector – perhaps it helps that he shares several traits with the 16th president.

Tall and lean (Lincoln was 1.93 metres in an era when the average man was 1.7 metres), Day-Lewis is also exceedingly courteous, spikily intelligent and seductively articulate, as one might hope from the son of a poet laureate. He would sooner allow the room to fall into silence, while dropping his head into his hands and massaging his forehead – presumably assisting the thought process – than fill the space with an unconsidered response. Although a serious man, he is not the least bit dour, given to throwing his head back and laughing heartily if something really amuses him.

Lincoln himself was known for his sense of humour; an uncommon trait in his day. Bob Mankoff writes in The New Yorker that a journalist covering a series of public debates in 1858 complained: "I could not take a real personal liking to the man, owing to an inborn weakness for which he was even then notorious and so remained during his great public career, he was inordinately fond of jokes, anecdotes, and stories."

The role is not, of course, just a case of Day-Lewis playing himself, as he is the first to admit. "[Lincoln's] capacity for logical, objective thought – a measured thought process leading toward a conclusion, from which you might make a decision, even one of vital national importance – that's something that's completely alien to me because I'm not a great logical thinker," he says.

Day-Lewis's preparation is legendary (and possibly, at times, apocryphal). He is said to have stayed so resolutely in character during the filming of My Left Foot, in which he played disabled writer and painter Christy Brown, that he had crew members feed him between takes. As native American Hawkeye, in The Last of the Mohicans, he reportedly lived on the land in the Alabama wilderness. And for the role of gang leader Bill the Butcher in Gangs of New York, he took butchering lessons, sharpening knives between takes. For every role there is a tale that simultaneously inspires awe at his commitment and a degree of sympathy for his fellow cast and crew.

"I'm always a little bit evasive about [my preparation], because I feel the minute you start to reduce something down to its component parts it's already misleading, because it's not really the way I work," he says. "To make kind of a list of things you did or needed to do, it kind of denies the overall sense in which you try to move towards the understanding of a life."

He will simply say that to find his way into the role of Lincoln, he read. A lot. "Probably rarely has there been a legacy of somebody's writing that told you so much about them as a human being," he says.

Day-Lewis set about learning several of those pieces and read them daily, aloud. "Lincoln used to read aloud . . . because he felt that he got a double benefit from that, because he was learning through his eyes and through his ears at the same time," says Day-Lewis, laughing fondly.

The reedy and slightly worn voice the actor settled on for the character, (a "Kentucky-Hoosier twang", according to one historian), has stirred a great deal of controversy in the US, where there is an expectation a great leader will have an authoritative baritone.

The first person to hear that voice was Spielberg, who received a cassette tape in the post one day, in an envelope with a skull and crossbones drawn on it (an indication, Spielberg has said, that it was for his ears only).

"Daniel in his role was the Abraham Lincoln of my fondest hopes and dreams," Spielberg says. "He was invested in the character and he was surrounded by other actors who invested themselves in their characters."

Among these are Sally Field ("who renders herself so open in the most vulnerable way through her work," says Day-Lewis), as Mary Todd Lincoln, unravelled by the grief of losing two children, plus a star turn by Tommy Lee Jones as abolitionist Thaddeus Stevens. "There is an orator in Tommy that is not often unleashed on the world because of the taciturn characters he tends to portray in his motion pictures," Spielberg says.

To assist in maintaining a certain period decorum, Spielberg – known for his "uniform" of jeans and baseball caps – wore a suit on set every day and addressed the actors by their character names, only ever calling Day-Lewis "Mr President", even between takes.

Although filming wrapped many months ago, it is clear Day-Lewis and Spielberg remain profoundly touched by the sense of intimacy, regard and affection that grew in them for Lincoln.

"I do grieve that I'm not in process with Lincoln any longer," Spielberg says. "I miss Lincoln and I miss everybody."

Day-Lewis agrees, adding he is grateful to Spielberg for allowing him to "spend this time with that man". "I will, I know, for the rest of my life regard this as having been one of the great privileges of my life, that's just a fact," he says. "After which it's hard to imagine quite what I'm going to do with myself."

Lincoln opens on February 7.