Recently the presidential campaigns have been turning to talk of the candidates' religious faith. Barack Obama proclaims a "personal relationship" with Jesus Christ. Democratic candidate John Edwards is on the religious offensive, speaking for Jesus himself when he tells an interviewer he thinks Christ "would be appalled" by our current policies regarding poverty and the war. Even the candidate who is arguably the least religious of the frontrunners--Rudy Giuliani--feels compelled to defend himself publicly on questions of whether he is "Catholic enough."

The salience of religion in our presidential politics perplexes Europeans, who generally see religion as a weird relic from the pre-scientific past. If Angela Merkel or Nicolas Sarkozy had made public statements during their campaigns about their personal relationship with Jesus Christ, it probably would have ended their political aspirations right then and there. As the head of a French think tank put it, "The biblical references in politics, the division of the world between good and evil, these are things that [Europeans] simply don't get. In a number of areas, it seems to me that we are no longer part of the same civilization."

This is now hyperbole. According to data from the 2002 International Social Survey Programme, an American is four times likelier than a Frenchman to attend a house of worship regularly, and eight times likelier than a Norwegian. Europeans are more likely to disdain faith openly: In 1998, the average Dane was seven times likelier than an American to agree that, "Religions bring more conflict than peace."

Many secular Americans envy the nonreligious Europeans and look expectantly to the day our presidential candidates finally abandon once and for all tortured religious rhetoric and focus on the earthbound business of human politics. This is not just evident from the lawsuits challenging the constitutionality of public manifestations of religiosity. The free market reveals it as well--witness the best selling success of recent books that make the case for atheism and rail against religion in public life, such as Richard Dawkins's "The God Delusion" and Christopher Hitchens's "God is not Great."

Markets don't lie: Lots of Americans are obviously sympathetic. Yet in all likelihood religion will grow as a social force in American culture and politics over the coming decades. The reason: A secular nation needs secular citizens. And nonreligious Americans are outstandingly weak when it comes to the most efficacious way to achieve this: by having kids.

If you picked 100 adults out of the population who attended their house of worship nearly every week or more often, they would have 223 children among them, on average, according to the 2006 General Social Survey. Among 100 people who attended less than once per year or never, you would find just 158 kids. This 41% fertility gap between religious and secular people is especially meaningful because people tend to worship more or less like their parents. According to data collected in 1999 by Gallup, 60% of adults who were taken to church at least once per month as children grew up to attend at least this often; only 15% stopped attending as adults.

The demographic implications are even more profound for the political left, where a disproportionate number of secularists are located. Religious people who call themselves politically "conservative" or "very conservative" are having, on average, an astounding 78% more kids than secular liberals. Studies show that people are even more likely to vote like their parents than they are to worship like them. The secular left, therefore, has to rely on the tough slog of bringing people from the political and religious middle over to their views. The religious right simply has to keep having lots of babies.

In short, unlike Europe, there is no indication that the competitive market for souls will shrivel any time soon. And candidates likely will be demonstrating their religious credentials for many elections to come.

Arthur C. Brooks is a visiting scholar at AEI.