In Italy, as in other countries around the world, recent reforms share the goal of increasing the fiscal autonomy of lower tiers of governments, from Regions to Municipalities, in order to align spending with funding responsibilities and increase the efficiency in the provision of essential public services. The purpose of this paper is to assess spending efficiency of local governments and to investigate the effects of tax decentralization, focusing on the role played by incumbent politicians' accountability. The analysis relies on a sample of Italian municipalities and exploits both parametric (SFA) and nonparametric (DEA) techniques to study spending inefficiency and its main determinants. Consistently with modern fiscal federalism theories, our results show that more fiscally autonomous municipalities exhibit less inefficient behaviours. We also find that the shorter is the distance from new elections, the higher is excess spending, thus giving further support to the traditional "electoral budget cycle" argument. Other political features of governing coalition, such as age and gender of the mayor, do not seem to exert any significant impact on inefficiency levels.