American presidential elections always produce their bizarre surprises, but few could have predicted that a row over the funding of birth control should be overshadowing the state of the economy as the focus of a heated national debate about religious freedom. Or to accusations that President Obama is engaged in an all-out "war on religion".

Yesterday Mitt Romney, looking ever more vulnerable to the socially conservative Rick Santorum, was answering audience questions in Michigan ahead of next week's primary -- one of those contests invariably described as "crucial". He took the opportunity to burnish his "pro-life" credentials, pledging for example to cut off federal funding for the abortion provider Planned Parenthood and promising to choose a pro-lifer as his running mate. He also spoke, not for the first time, of the need to protect "religious freedom". Criticising Obama's record, he put much of the blame on "the people the president hangs around with and their agenda, their secular agenda". They were people who "fought against religion".

This is, of course, code for the administration's policy, since watered down (largely under pressure from the Catholic Church) to force even religious employers to provide contraceptive coverage as part of their workers' health insurance. The ultimate problem might lie in the concept that healthcare provision should form part of the employer-employee relationship at all. There's no doubt, though, that an ad hoc alliance of Catholic bishops, Protestant evangelicals and Republican politicians has managed to turn this from an issue of equal access to healthcare into one of "religious freedom", at least in terms of the public debate.

Even though the freedom under discussion is not the freedom of citizens to worship freely but rather the freedom of powerful religious organisations to deprive ordinary Americans of provision that most of them have for decades taken for granted. Even though most ordinary Catholic voters disagree with their church leadership on the issue.

When Romney speaks of a "secular agenda" what he is actually talking about is the rights of women to have control over their own bodies and their own fertility. The vast majority of American women, including Catholics, have long used contraception in their own lives, whatever the official position of the church hierarchy. Romney himself, when he was governor of Massachusetts, took a far more nuanced position on abortion than the one he now advocates. It's fair to say, though, that his current pro-life stance long predates the emergence of Rick Santorum as a serious contender. He has been accused of flip-flopping, but it would probably be truer to observe that his shift mirrors the reorientation of the Republican party as a whole in recent decades.

As Ann Gerhart noted the other day in the Washington Post, there was a time when a Republican congressman from Texas (by the name of George Bush Sr) could argue that "if family planning is anything, it is a public health matter." That was the 1970s.

For all the heightened talk of a "war on religion", it's hard to see how the the Obama administration represents an atheistic lurch. As both candidate and president, Barack Obama has "done God" with the best of them. The US constitutional tradition, embodied in the First Amendment, has always stressed freedom of religion rather than (like French secularism) freedom from religion, but from the days of the Founding Fathers until well into the second half of the twentieth century, politics and religion were seen as largely separate spheres of activity. John F Kennedy's opponents tried to discredit him by hinting darkly that, as a Catholic, he might be taking orders from Rome. Today's Republican hopefuls, even the Mormon, seem almost to want to present themselves as instruments of Vatican policy. All very strange.

It's actually the Obama administration, insofar as it is pursuing a "secular agenda" at all, that stands in the mainstream of US political and legal history. A secular agenda is not the same thing as an anti-religious one, a fact that would have been obvious to every previous American generation. What is historically novel is the attempt on the part of the religious right to recast political questions as spiritual ones. They are trying to use the hallowed constitutional right to freedom of worship to restrict the freedoms of ordinary Americans, religious and otherwise. And, at least in the limited area of the race for the Republican nomination, they would seem to be making most of the running.

George Bush Sr, in the speech quoted above, could refer to opponents of state funding for birth control as "militants" who sought to use the issue as "a political stepping stone." Forty years later, it seems, the militants have taken over the Republican asylum.