JUST five months after May’s election Belgium has a new government. Set against the 18 months that it took in 2010, that is fast work. Charles Michel, the 38-year-old leader of the French-speaking liberals, will lead a four-way coalition consisting of his party, the Flemish liberals, the Flemish Christian Democrats and—for the first time—the Flemish nationalist N-VA party. As the largest party, the N-VA, led by its bullish leader, Bart De Wever, is now Belgium’s dominant political force. And that shreds nerves among those fearful of the country’s possible break-up.

Founded on a platform of separatism, the N-VA has long exploited the deep cultural and linguistic chasm in Belgium. The people of the two biggest regions, Flanders and Wallonia, tend to see themselves as Fleming or Walloon first and Belgian second, if at all. The divide is entrenched in a political system that splits into Dutch- and French-speaking parties.

A lattice of federal, regional and municipal governments binds Belgium together, but economic forces are pulling it apart. Belgium’s public debt, at over 100% of GDP, is among the European Union’s biggest, and the economy grew by a meagre 0.2% in 2013. Rich citizens in Flanders are tired of high tax rates, rising social-security costs and the subsidies that they pay to support their poorer neighbours in Wallonia.

Separatism took a back seat to the economy in the election as Mr De Wever painted the Francophone socialists, led by Elio Di Rupo, as a drain on prosperity. “Autonomy was no longer presented as a goal in itself, but instead as a means of implementing a right-wing economic policy that Flemish people actually voted for,” says Dave Sinardet of the Free University of Brussels. The party promised tax and benefit cuts and an end to automatic wage indexation. In the coalition talks Mr De Wever dropped demands for more devolution in favour of his economic agenda.

Joining a coalition with him is still a huge gamble for the French-speaking liberals. Francophone critics complain that the party has betrayed its previous commitment not to work with the nationalists. They say Belgium’s stability is threatened by a coalition with the support of only a minority of French-speaking parties. Moreover, Wallonia is now represented by different parties at the federal and regional level, a recipe for obstructive infighting.

The choice of the youthful Mr Michel, who looks strikingly similar to his father Louis, a former foreign minister and European commissioner, is meant to soothe Walloon anxieties. With an eye on France, the coalition promises to eliminate the budget deficit by 2018 rather than 2016, as previously planned. The main burden of fiscal consolidation will fall on spending. The parties have agreed to cut taxes on labour, except for health insurance, and increase the retirement age from 65 to 67.

Mr De Wever has ambitions to entrench N-VA as a national movement, not just one seen as a regional force intent on Belgium’s destruction. Whether he succeeds in this will affect his commitment to the country as a whole. If Mr Michel’s liberals or the centre-left manage to block him, some nationalists will revert to what they have always believed: that in Belgium it is not right v left but Fleming v Walloon.