Polyaniline thin films can serve as material for electrochromic devices, due to the displayed color depth and the rapidity of passage from one color to another. The changes of optical density are particularly interesting in a pH 3 electrolytic medium. In this medium, the films were characterized by Raman and optical (optical multichannel analysis, OMA) spectroscopies and the film stability during different kinds of cycling (for cycles up to 10,000) was investigated; the role of anodic reverse potential was emphasized. The use of a mathematical spectra decomposition allows us to arrive at a semiquantitative Raman analysis, showing the increase of polaron sites during cycling. The analysis of the spectral structure of the polaron optical absorption band, during the polymer equilibration at the coloration potential (obtained owing to OMA) allows us to relate the degradation mechanisms to the organization in bipolarons, followed by their scattering in isolated sites.