ACROSS western Europe, parties of the centre-left have struggled to make sense of the fact that Islam is a growing cultural force in their continent. At times, the relationship has veered between close embrace and secularist recoil. But parties of the left will lose out politically unless they can find a way to give Muslims the opportunities to participate in public life that other religious groups already enjoy. That, in a nutshell, is the argument laid out by Jonathan Laurence, a professor at Boston College, in the latest issue of Dissent, a quarterly journal. As one of the most thoughtful observers of the politics of European Islam, he makes some important, paradoxical points.

When poor immigrants of Muslim heritage started coming to work in Europe's factories half a century ago, they were welcomed by leftist parties as victims to be defended and promising political allies. But the relationship went sour after Muslim migrants showed their traditionalist side: burning the books of Salman Rushdie, the writer whose death was demanded by the Ayatollah Khomeini, and insisting on traditional headgear for women.

The centre-left has an ambivalent attitude to religion in general. It was once said of Britain's Labour party that, although it was a "broad church", it owed more to Methodism than to Marx. But in most other European countries, social-democratic parties have occupied the secularist ground, in opposition to the moderate religious conservatism of the centre-right. When centre-leftist parties have tried to reach out to Muslim voters, they have sometimes been burned by the experience. Earlier this year, a Muslim member of Sweden's Social Democratic party had to quit the leadership after making a reference to attacking Israel.

The paradox grows sharper, as Mr Laurence points out, when you look at voting patterns among Muslim migrants in Europe. In their new homelands, they still generally vote for centre-leftist parties (unless there a strong reason not to, like the Iraq war), but if they remain active in the politics of their mother country, they lean towards Islamist conservatism. The Islamist parties of Turkey and Tunisia do even better in the European diaspora than they do at home, Mr Laurence notes. (He could have added that the Islamists of Bangladesh do better in east London than they do in Dhaka.)

Although his broad-brush analysis of the European scene is clear and persuasive, some readers will part company with Mr Laurence's conclusion. Despite the relationship's inherent problems, he argues, the centre-left may lose out electorally unless it somehow re-engages with Islam. "When the left 'bets against God'....[it] forgoes potential alliances with faith communities that share common moral, economic and social ground."

In Britain at least, it looks likely that the centre-left will continue to swing erratically between cultivating Islam and cultivating wariness of Islam. In recent days Labour's education spokesman, Tristram Hunt, has scored points over the strange goings-on at the Al-Madinah school in Derby, which asked all prospective women teachers, Muslim or otherwise, whether they would be prepared to cover their hair. This establishment, excoriated in an inspectors' report this week, was a perfect example of the flaws in the Conservative-led government's policy of allowing "free schools" with weak supervision: by making that argument, Mr Hunt will please some citizens and alienate others, including Pakistani-born voters who have reacted defensively to criticism of the school. In the confusing, multicultural Europe of 2013, a politician or political party cannot please everybody and perhaps should not try.

