PARIS — I’ve lately been telling French people about the Hail Mary pass. I explain that it’s a desperate move in American football: You’re running out of time to score, so you lob the ball toward the end zone and hope for the best.

The ’ail Marie — as I’ve been pronouncing it — is the best metaphor I’ve found for the French elections this Sunday. The country that gave us the Enlightenment, Cartesian logic, the Napoleonic Code and possibly reason itself may be about to just throw a ball into the distance and see what happens.

Proof of this is the sudden rise of Jean-Luc Mélenchon, until recently an angry ex-Trotskyist on the left wing’s colorful fringe. He probably never thought his policy ideas — like cutting the workweek to 32 hours (from a punishing 35), letting everyone retire at 60, and possibly leaving the European Union and joining an alliance with Venezuela and Cuba — would need to pass a reality test.

Now he’s one of the four candidates who are neck-and-neck, in a race where a third of voters say they might still change their minds. Thursday night’s shooting on the Champs-Élysées — apparently another act of terrorism here — makes the results even more uncertain.