THE script for France’s presidential election was supposed to be clear. Investors accepted that Marine Le Pen, the anti-European Union, pro-Russia, far-right candidate, would make it through to the second round. But markets presumed that, just as when her father made the second round in 2002, voters would flock to the alternative candidate, either François Fillon, a Catholic conservative or Emmanuel Macron of the centre-left. There was a risk of a Brexit-style upset but most investors seemed confident that Ms Le Pen will be stopped.

But the worries are mounting again. That is because a new possibility has emerged. Jean-Luc Mélenchon of the far left was perceived by TV viewers to have won the latest debate and seems to have gained voters from his Socialist rival, Benoît Hamon. Mr Mélenchon is now at 18% in the latest poll in what is a tight four-way race; only six percentage points separate the top four candidates. If Mr Macron’s more left-wing supporters switch, then it is possible to imagine a Le Pen-Mélenchon second round.

In economic terms, investors would be faced with an unpalatable choice. Ms Le Pen has talked of reviving the French franc, and redenominating government bonds in that currency; an effective default. Mr Mélenchon wants a salary cap, a 32-hour working week, a retirement age of 60, nationalisation, to leave NATO and renegotiate EU treaties. Polls suggest Mr Mélenchon would beat Ms Le Pen (one poll has him winning 57% to 43%), not least because he lacks her racist views. Success for either candidate would immediately lead to another EU crisis that might be even greater than 2011-2012; France is a core member of the union. Mr Mélenchon sees himself as the French Hugo Chávez; if any French voters have forgotten what Chávez did to the Venezuelan economy, see the Free exchange column in our latest issue.

The spread (excess interest rate) paid by France to borrow over ten years relative to Germany is now three-quarters of a percentage point (75 basis points), up 40 basis points over the last 12 months. More investors are hedging against euro risk, as measured by the implied volatility in the options market. These crisis measures are still below 2011-12 levels, indicating investors don’t believe the nightmare option will happen. Citigroup puts the various candidates’ probability of victory at Mr Macron (35%), Mr Fillon (30%), Ms Le Pen (25%) and Mr Mélenchon (10%). This seems strange given that Messrs Fillon and Mélenchon are essentially tied in the polls.

Perhaps investors are counting on candidates being less radical in office than they are on the campaign trail. And even if the far-right and far-left candidates win, it is not clear whether they could push through their programmes; they are unlikely to have a parliamentary majority. Mind you, that is also true of Mr Macron, whose En Marche! party, is a start-up. Much uncertainty lies ahead. And that points to a lot more market volatility.