MARINE LE PEN and her far-right National Front (FN) began December looking like the leaders of a new wave of European populist nationalism. They were on the verge of winning two of France’s regional elections and upsetting the country’s traditionally bipartisan politics. Instead, mainstream parties manoeuvred to keep the FN out. Now some on France’s centre-left hope this strategy could signal a deeper realignment. That is less far-fetched than it sounds. With many European countries facing populist insurgencies, parties of the centre-left and centre-right find themselves co-operating to hold off the upstarts. The FN under Ms Le Pen, a softer version of the xenophobic party founded in 1972 by her father, Jean-Marie Le Pen, came top in first-round voting to regional assemblies on December 6th. The party notched up a record 40% in the north, where Ms Le Pen ran, and the south, where her 26-year-old niece, Marion Maréchal-Le Pen, did. These leads did not translate into a single victory at second-round voting on December 13th, chiefly because of a tactical decision by the governing Socialists to sacrifice their own candidates. Manuel Valls, the prime minister, ordered Socialists in three regions where the rival centre-right looked the stronger opponent to pull out (one refused). This, combined with some scaremongering—he warned of “civil war” should the far right win—helped to get voters out, and to thwart the FN.

It would be a mistake, however, to conclude that the FN has been fatally weakened. It drew 6.8m votes in the second round—up from 6m in the first, and 400,000 more than Ms Le Pen scored at the presidential election of 2012, when turn-out was higher. Except in small constituencies, the party struggles to win a majority, and Ms Le Pen’s chances of becoming president remain slim. But she did win 42% in her region, and her niece 44%. The FN’s national second-round score of 27%, were it to be repeated in the first round of the presidential election in 2017, should be enough to secure Ms Le Pen a place in the run-off.

The bigger question is whether the rise of the far right could force mainstream parties to shift towards more bipartisanship. Mr Valls called this week for a different form of post-sectarian politics, in which opponents work together for the general interest. A centre-left politician with close links to Michel Rocard, a moderate former prime minister, Mr Valls has long craved a larger political centre. He has argued that it was a mistake not to have opened up to François Bayrou, the leader of a centrist party, after François Hollande was elected president in 2012.

That French voters, especially the young, rallied to block the FN suggests that left and right can unite against a common opponent—as they did in 2002, when leftists voted for Jacques Chirac, the centre-right candidate, to defeat Mr Le Pen after he unexpectedly squeaked through to the second round of the presidential race. In many ways, voters who backed the two main parties differ less from each other than from FN supporters (see chart). Voters without a high-school qualification are more than twice as likely to plump for FN as those with a degree. Both left and centre-right, by contrast, are more favoured by the better-educated.