Upon suggesting that Yom Kippur ought to be made a national holiday in France last month, Eva Joly - candidate for Les Verts - was briskly condemned by the left, the right and the far-right. Marine le Pen went so far as wonder aloud: "I have to ask myself if Eva Joly finds anything good in France, our people, traditions, history and life morals".
François Hollande's just-published campaign manifesto - his 60 "engagements" or pledges - reinforced what his spokesman called "the great French principle of secularism", laïcité, by proposing the constitutionalisation of the 1905 law on separation of church and state. Nicolas Sarkozy shot this down as a "fundamentalist vision of laïcité", arguing that codification would "exclude from the public sphere references to the cultural or intellectual elements of religion".
At present, laïcité demands the total exclusion of the church, synagogue or mosque from the affairs of state, treating all religions equally and granting none special rights or privileges above any other. Elevating Yom Kippur to the status of a public holiday would directly challenge this secular status quo.
The oddity is that debate over Yom Kippur - or indeed the decision in 2004 to outlaw the wearing of the yarmulke in public schools - does not indicate any national anxiety over the assimilation of French Jewry.
Even taking account of the sizable influx of Sephardim from the Maghreb during the 50s and 60s, Jews in France have adapted in the same way as those in other Western nations.
Rather, the principal concern is Islam: Jonathan Meades, in his recent documentary on France, argued that post-colonial immigration has challenged French monoculture. For some, Islamic public prayer or women veiled in a niqab are affronts to Frenchness itself, and an inclusive national identity that is supposed to supersede faith as a form of identification.
Sociologist Martine Cohen argues that, in the current environment, the right for French Jews to express individual belief or convey difference has been undermined. What Sarkozy seems to indicate is that laïcité must protect fundamental French values while finding a way to accommodate individual self-expression and religious thought, not only for Jews but for all of France's religious communities.