Politics by denunciation: political whistleblowing against members of parliament in Italy

Judicial investigations into politicians are a fundamental component of politics, with these investigations often leading to public scandals. Yet, empirical evidence of the strategic determinants of judicial investigations is intrinsically hard to gather, a problem that has significantly limited the study of this important phenomenon. This paper studies the politics behind judicial investigations by leveraging new data on prosecutors’ informants in 1125 episodes of misbehavior of Italian MPs involved in different crimes (1983–2019). Results provide evidence in favor of a political use of denunciations for corruption crimes: when a party weakens, the likelihood that political enemies denounce past misbehavior of members of the weakened party increases, suggesting that the political use of denunciation is elastic to changes in the electoral performance. Furthermore, weakened MPs are more likely to be accused of misbehavior that happened a long time before the accusation, which further supports the argument that accusations are politically motivated.