Within a one-dimensional spatial framework, we deduce that parties’ incentives ‘to go negative’, by blaming alleged insufficiencies of the rival concerning commonly shared values, increase with their ideological proximity. We test our hypothesis by considering the long period of no-cabinet alternation that characterized both Italy and Japan. In particular, we focus on the (spatial) incentives of the Italian Communist Party and of the Japanese Socialist Party to emphasize on a particular topic related to negative campaigning, i.e. political corruption issues. The status of the perennial opposition held by both parties, together with the existence of several political corruption scandals during the period considered, makes the Italian and the Japanese political systems particularly apt to test our hypothesis. The results, based on data derived from electoral programs, support our theoretical insights.