It may not decide who is to become the next President of the United States, but abortion is once again a hot issue as the 2008 election campaign is launched at the conclusion of the two party conventions. As during the campaign between John Kerry and George W. Bush four years ago, so attention has again focused on the Catholic vote - approximately a quarter of the whole - and how it will be affected by the strongly expressed opinions of some leading members of the Catholic hierarchy. Joe Biden, the man chosen to be vice-presidential running mate for the Democratic candidate, Barack Obama, is, like Mr Kerry, an Irish-American Catholic who supports - in a qualified way - the pro-choice position.
The stance taken by socially conservative prelates such as Archbishop Charles Chaput of Denver is that Senator Biden should not present himself for Holy Communion when he attends Mass, as he does every week. Indeed, he should be refused Communion if he insists on doing so. The fact that Senator Biden has opposed the legalisation of partial-birth abortion and is also against government funds being made available for abortion has not won him a reprieve from Archbishop Chaput's censure. But it may help him with Catholic voters in general, who by no means always do what their bishops tell them to. A significant number of them were persuaded to swing towards Mr Bush in 2004, but many have since noticed that America's pro-abortion laws are no nearer repeal as a result.
No doubt one of the reasons why the Republican candidate, John McCain, has chosen Governor Sarah Palin of Alaska is because she is strongly anti-abortion and therefore thought to be a magnet for conservative Catholic and Evangelical voters. But this is an area where the Catholic position itself is more nuanced. Whether or not a particular Catholic politician does or does not receive Communion is an issue that can cause hurt and embarrassment. But it does not stop Catholics from voting for him or her, even on a strict interpretation of moral theology and canon law. As Cardinal Ratzinger, Pope Benedict gave a ruling in 2004 that generally supported the case for adamantly pro-abortion Catholic politicians being denied Communion, but he added: "When a Catholic does not share a candidate's stand in favour of abortion and/or euthanasia, but votes for that candidate for other reasons, it is considered remote material cooperation, which can be permitted in the presence of proportionate reasons." This deserves to be more widely known, and is equivalent to the repeatedly stated view of the English and Welsh bishops that "a general election is not a single-issue referendum". Senator Biden has certainly been pro-life in urging outside intervention to stop genocide in Bosnia and Darfur, issues on which conservatives tended to be more restrained. He supports such pro-life causes - although not usually seen as such - as universal health care and measures to improve the lot of the American poor, among whom infant mortality runs at rates more usually seen in the developing world.
The demand that the Church should stay out of politics is transparently unreasonable. But if Catholic bishops are to exert political influence they must do so with a sophisticated appreciation of complex issues. If they are not careful, church leaders can find themselves being cynically manipulated by those whose real interest is not morality but power.