In a fascinating piece on the recent presidential elections in France, French political analyst Michel Gurfinkiel contrasted the fortunes of left and right in the 18th and 17th districts in the north of Paris. The 18th voted overwhelmingly for the left; the 17th for the right.

With no significant socio-economic differences, what could explain such radically contrasting voting patterns? The answer, Gurfinkiel said, was the distinct "ethnic and cultural" make-up of the two areas. In other words, the 18th district is mostly Muslim and "neo-French"; the 17th is not.

Recognition of the alliance between political Islam and the ideological left is not new, of course. It was gestating as far back as the 1960s when writers such as Herbert Marcuse sought to harness the revolutionary potential of third world movements that the Western proletariat had so conspicuously failed to provide.

Following the end of the Cold War, and especially after 9/11, it became clear that the anti-Western ideology par excellence was going to be Islamism. With more than a billion potential adherents, this was a force to be reckoned with. And if the price of the alliance was dropping or de-prioritising support for the rights of women, gays and, of course, the state of Israel and Jews in general, then so be it.

What is new is that this alliance is now starting to be politically significant in European electoral politics. In countries with large and growing Muslim populations - in France, Muslims make up at least 10 per cent of the population - capturing the Muslim constituency may already be a factor in determining the overall result.

There are no ethno-religious breakdowns of the vote, but given the narrowness of his victory - Francois Hollande won 51.6 per cent to Nicolas Sarkozy's 48.4 - it is quite possible that, in the absence of a sizeable Muslim population, Sarkozy would be breezing into his second term.

It is a staggering thought, and the implications are vast.

France's Jewish community, for example, has largely been reasonably well-integrated into mainstream politics and society, despite a strained relationship between France and Israel for decades, more or less regardless of whether left or right held power.

But if we have now reached a tipping point where it is no longer possible for left-wing parties to win elections without retaining the bulk of the Muslim vote, the future for French Jews, especially those with a strong affinity for Israel, may be bleak.

This is not to say that French Muslims are only concerned about Israel. Like their non-Muslim counterparts, they vote on a variety of issues. But the Palestinian cause is clearly something that they and their communal leadership care about deeply. And if I can work out what that implies for French policy towards Israel under Francois Hollande, you can be sure that his strategists can work it out too.