In 2012 Lang was chosen as the Socialist Party candidate for the National Assembly in the second district in the Vosges department. A controversial figure in the Socialist Party since his collaboration with Sarkozy, Lang's constituency was abolished during the national reapportionment and he failed to be nominated in several other constituencies before finally succeeding in the Vosges. The electorate in this department is considered by observers to be more conservative than in Lang's previous seat. Lang was criticized for being an 'outsider', to which he countered that he had been born in the region. Lang was narrowly defeated on the second round of voting in the election on 17 June 2012, winning 49.1% of the vote.