Sochaux moved a step closer to safeguarding their own Ligue 1 future while almost certainly condemning Nantes to a second relegation in three seasons.
Goals from Mevlud Erding and Rabiu Afolabi give the Montbeliard side a good chance of survival with one game to play - but for Les Canaris, a failure to find only a second win in 15 games proved costly.
Although Mamadou Bagayoko pulled a goal back from the penalty spot, Elie Baup's team need to win their last game of the season and hope Caen and St Etienne both lose, while also hoping for a 16-goal turnaround on the northern side.
If Sochaux survive, it is unquestionably their form at the Stade Auguste-Bonal which is the reason - they have lost just four of their 19 matches there this season.
They started strongly tonight and after only three minutes Nantes goalkeeper Jerome Alonzo had to be alert to deny Vaclav Sverkos after a Stephane Dalmat free-kick had deflected to him.
Three minutes later Alonzo just beat Afolabi to the ball, before Nantes created their first chance in the 16th minute when Teddy Richert did well to save Aurelien Capoue's well struck shot.
Turkey's Erding made the vital breakthrough 10 minutes before the interval, heading a Marvin Martin free-kick convincingly past Alonzo.
And Afolabi doubled the advantage just before half-time. A Martin free-kick was again the source, with Nigerian Afolabi collecting the ball and beating Alonzo with another powerful shot.
Nantes were thrown a lifeline on the hour when Bagayoko wrong-footed Richert from the penalty spot, after Afolabi had fouled Ivan Klasnic.
Sochaux came close to restoring their two-goal advantage soon after when Ryad Boudebouz's free-kick was only marginally off-target.
Yet the visitors finished strongest, with Capoue volleying against a post 10 minutes from time and Djamel Abdoun bringing a good save out of Richert in injury time.