Proto_Spark posted... Though the worst attack ad in political history was probably attacking Jean Chretiens deformity (for anyone unaware, in 1993 the Progressive Conservative party effectively sent out an attack ad making fun of a deformity Jean Chrtien had due to suffering from Bells Palsy. People were disgusted and Chrtien handily won the next election and was PM for the next decade)
Wow, it even has its own wiki page:
https://en.wikipedia.org/wiki/1993_Chr%C3%A9tien_attack_ad---
River Song: Well, I was off to this gay gypsy bar mitzvah for the disabled when I thought 'Gosh, the Third Reich's a bit rubbish, I think i'll kill the Fuhrer'