A capacitor assembly that is capable of exhibiting good properties under humid conditions. The ability to perform under such conditions is due in part to the use of an intrinsically conductive polymer in the solid electrolyte that contains repeating units having the following formula (I): wherein, R is (CH2)a—O—(CH2)b; a is from 0 to 10; b is from 1 to 18; Z is an anion; and X is a cation. Due to its unique structure, the polymer is not highly sensitive to moisture. Consequently, the resulting capacitor assembly may exhibit excellent electrical properties even when exposed to high humidity levels.