Fortunately, at 75, Stark is not planning to seek higher office. If he had been, he had just committed political suicide. Being an atheist is the biggest handicap a person could have to being elected US president - worse than being gay or a woman, according to a Gallup poll in February.

More than 53 per cent of people surveyed said they would not vote for an atheist. They would prefer a homosexual president - 43 per cent said they would not vote for a homosexual - or a woman president (11 per cent said they would not vote for a woman). And it seems that these days being black or Catholic or Jewish is hardly a barrier at all, with each of these factors being named as a bar by fewer than 7 per cent of voters. That the US remains so concerned that its leaders be people of faith is surprising.

In most industrial societies, the level of religiosity declines as the society becomes wealthier and more sophisticated, according to John Green, a senior fellow at the Pew Forum on Religion and Public Life, which regularly surveys attitudes towards religion in the US. Yet the US remains a highly religious place. Not the most religious place on the planet, but certainly more religious than Europe and Australia.

Green puts that down to America's historical roots. "Many people came to America precisely because they can practise their faith openly," he says. "Secondly, these extensive religious communities compete with each other for members. It means more effort goes into recruiting and maintaining members." There is also a kind of counterintuitive argument about why religion has flourished, according to Green. Because of the separation of church and state, churches have had to build extensive private organisational structures to push their interests and so have become strong within the society. One such manifestation of that organisational power is the Southern Baptist Convention, a powerful wheel in the evangelical movement. Dr Richard Land is president of its Ethics and Religious Liberty Commission and a close friend of President George Bush.

He is not surprised that Americans want a president of faith. "Being elected president is more like a date than a job interview," he says. "I think that given that 91 per cent say they believe in God, most Americans are more comfortable with a person that acknowledges a higher authority other than themselves. It would take a very charismatic atheist to convince people to vote for them."

In 2000 and again in 2004, Bush, a born-again evangelical, tapped into the Christian right movement and narrowly won. According to Land, 78 per cent of white evangelicals voted for Bush, making up 26 per cent of all votes cast. Whether the Republicans are successful in marshalling the conservative Christian right again will depend on who they select as the nominee, he says, warning that selecting a pro-choice candidate such as Rudy Giuliani will shatter that bloc of votes. Pew's work confirms that Republican voters are more religious than Democrats, but 62 per cent of Democrats say they have no doubt that God exists, and they pray regularly.

The Democrats are determined to ensure that faith is not the sole preserve of the Republicans next year - and the Republicans are equally determined not to lose the Christian vote. In June the TV news network CNN staged a special forum co-hosted by the Sojourners, a liberal Christian organisation, between the three Democrat frontrunners. Hillary Clinton was asked whether her faith had helped her get through Bill Clinton's infidelity. She said she felt a little uncomfortable talking of such matters, but noted people seemed to take these issues of faith more seriously than they did a decade ago.

In Republican debates, candidates have been quizzed about whether intelligent design should be taught in schools alongside Darwin's theory. Three candidates said they did not believe in evolution at all. Mitt Romney, a Mormon, has faced questions on how the Book of Mormon would inform his decision-making as president, while the thrice-married former mayor of New York, Giuliani, has been asked - and refused to answer - whether he was a traditional practising Catholic. Their respective baggage with Christian voters is continuing to fuel speculation that there is still room for a conservative candidate, such as the actor Fred Thompson or former speaker of the House Newt Gingrich. At the organisational level, Democrat Speaker Nancy Pelosi has led the way in forging ties with the more progressive Christian groups. As minority leader she initiated the Faith Working group of caucus, a largely behind-the-scenes endeavour that has been steadily building bridges with the progressive religious community as well as talking to lawmakers about how to communicate in a language that will appeal to the faithful - something Pelosi does well.

"The Democratic agenda is deeply rooted in faith, but we have been less effective than we could be in communicating how our moral values guide our policies," says the group's chairman, Jim Clyburn, an African Methodist Episcopalian from South Carolina. In the Democrat national headquarters, work is also under way on a full-blown strategy to ensure Democrats do not cede the faithful to the Republicans. In 2004 there was just one aide dedicated to mobilising religious voters. Now there is a faith advisory council from a group of 60 clergy and faith community figures, who have been trained to talk to the media about the Democrats' policies. There's also a team of consultants and a website that will soon be launched to help in the vote-gathering effort.

To Australians, the idea of asking a politician about their religious beliefs and practices would seem impertinent, at best irrelevant. Being a non-believer is certainly not a bar to high office as Bob Hawke proved. In 1980, during a interview on ABC television, Hawke admitted: "Until I get some evidence one way or the other which is compelling to me, I'm going to have to remain an agnostic …" He was prime minister three years later. In recent years, religion has made a few modest incursions into Australian political life. Family First, established by the former national director of the Assemblies of God, achieved the election of Senator Steve Fielding on a platform of family-friendly policies that would appeal to church groups. But Fielding and his party do not refer to religion as their moral guiding force, preferring to talk about the interests of families. Furious debates over moral issues such as embryonic stem cell research and the morning-after pill RU486 have also inevitably swept religion into the parliamentary chambers.

But ironically it has been the leader of the Labor Party - a party that prides itself on its secular nature - who has pursued a strategy of courting the religious vote. In 2005 Kevin Rudd, a committed Anglican, told ABC's Compass program it was the "right" time in political history. "And that is to engage this debate about faith, values and politics and not to vacate the ground for the other mob. For those on the political right who believe that faith is their natural preserve, I don't intend to stand around or let that happen. I've got a responsibility for the tradition of Christian politics that I come from," he said.

To date, personal beliefs are not put into the spotlight in the way they are in the US, but this federal election may break new ground. There are, however, some lessons for politicians in the US experience. Green says Pew's research consistently reveals an ambivalence that Americans feel towards the intrusion of religion into politics. Americans are comfortable with religious organisations expressing views, but not so keen on them getting directly involved in politics by, say, endorsing candidates from the pulpit, Green says. They are both uneasy with approaches offered by liberals and conservatives, Pew concluded in its 2006 survey. Some 69 per cent of Americans say liberals have gone too far in keeping religion out of schools and government, but the proportion of people who express reservations about attempts by Christian conservatives to impose their religious views has edged up in the past year, with 49 per cent of respondents expressing wariness about this.

It seems that Americans want a Christian president, but they are not sure that he or she should let their religious supporters have open access to the Oval Office.