If it is a good day, Iona is a good place to start. It has been mostly written about as a tranquil, historic island, the place where St Columba arrived with his mission, where kings were interred and poets flocked. And it is an almost unearthly place, whose green is more vividly green than elsewhere and whose sands are bone-white. It was well described by one island hero as being 'only a tissue paper separating earth from heaven'.
But Iona has been more. It is also the place from which one of the most turbulent and determined attempts in modern times was made to mingle politics and religion. The person who called the island 'tissue paper' was George MacLeod, the Church of Scotland minister, street preacher, socialist, a First World War hero who became a pacifist, and general troublemaker who, in 1938, founded the Iona Community. It rebuilt the ancient Abbey and pioneered a socially engaged mission which shook Scotland awake during the sleepy Fifties. MacLeod, who in later life sat as a cross- bench Peer ('getting crosser and crosser' he said), was both an inspired preacher and an enthusiast for every radical cause going.
Since his heyday, Britain become more secular and materialist. Neither politically-committed religious leaders nor religious politicians have enjoyed much popular success. Leftish archbishops, addicted to MacLeod causes, have failed to stop congregations thinning. On the other side, Tory Christians such as Johns Patten and Gummer have found their religious messages opened them to ridicule and attack.
All of which makes it more interesting that, when it comes to the Labour leadership, outspoken Christians are so much in evidence. No one was less 'churchy' than Mr Smith. But he went out of his way to insist: 'For me, socialism is largely Christian ethical values . . . Politics is a moral activity. Values should shine through at all times. You could call it evangelism or salesmanship. I want the spirit of the evangel, but the success of the good salesman.' (Mr Smith's Christianity was cited, by the way, in our coverage of his death, despite the assertion to the contrary by a clergyman in the letters column earlier this week. Let us hope, Rev Springbett, that your sermons are more meticulously researched than your epistles.)
Among the possible contenders to replace him, both Tony Blair and Gordon Brown have chosen to write and speak about the connection between their faith and their politics. Mr Blair has written that 'Christianity is a very tough religion . . . It is judgemental. There is right and wrong. There is good and bad.' Both he and Mr Brown have argued that the values of community and inter-dependence are central both to their faith and their socialism.
Clearly there is an element of risk for any politician who gets involved in 'God stuff'. We are a mercenary, easily-embarrassed lot, and Mr Smith's Christian Socialism might have backfired. He believed many City pay packets were immorally high. If that message had got through, it might have caused the Soft South to shiver and stay Tory. But there was a worldliness about Mr Smith that diluted any preachiness: most of the time he hid his Christian radicalism under good City cloth.
Mr Brown's public image is a touch dourer, at least in the eyes of southerners. For him, the public profession of Christian values must be partly a tactical dilemma, too: how strongly does he emphasise his 'son of the manse' Scottishness? Mr Blair's case is different again. Although educated in Scotland, and close to one of the kirk leaders who supported the Iona Community, he comes across as English. For him, the biggest risk in professions of faith is that they may emphasise his choir-boyishness and subtly reinforce doubt about whether he is ruthless enough.
Beyond the dilemmas for individuals there are wider questions. Does the proclamation of Christian morality reassure voters about leftish politicians, yet make them uneasy about Tory ones? Is there a sense in which uncommitted electors vote Conservative on practical and economic grounds (and so raise a sceptical eyebrow when told they are doing so as an act of morality), yet want to feel good about themselves if they vote Labour or Liberal Democrat? These are deep waters, and I am flinging wild generalisations across them.
But it may be that an intellectual tide is turning as voters look for alternative social values to those of the market. In yesterday's Independent, we reported the publication of a book from the Henley Centre for Forecasting which claimed to find a backlash against 'more competitive and divided ways of operating and living'. Its author argues that there is a gnawing unease about consumerism. One should be cautious: this may be nothing more than an effect of the business cycle. But the left's hopes of regaining power depend partly on voters being ready to look for alternative values.
Even when voters are themselves irreligious, they may be attracted to leaders who sing those old songs. The offer of Christian values is, of course, somewhat weaselly: it suggests the social effect of religion without the religion itself, a world without hell fire, but in which everyone behaves as if hell fire awaited.
Yet there is something in the air that is more than hypocrisy. There is a social unease, a searching for verities, expressed across the political spectrum, from the Prince of Wales to Tony Benn. Would professions of faith like those from Mr Smith, Mr Blair and Mr Brown have attracted so much interest in the Sixties, Seventies or Eighties? Would they have been made? Mr Blair recently asserted: 'Christianity . . . is about the union between individual and community, the belief that we are not stranded in helpless isolation, but both owe a duty to others as well as ourselves and are, in a profound sense, dependent upon each other to succeed'? A generation ago, those words would have seemed musty and out-of-touch. Today, they catch something in the public mood. Even for agnostics, Iona is not all that far away.