The city of Montevideo changed drastically during the last decade of the twentieth century. The number of informal neighborhoods increased in an unprecedented manner. Many of these neighborhoods started as organized land invasions, that is, with a group identifying a piece of land, invading it, outlining streets and plots, negotiating with authorities and organizing to demand public services. This article asks what explains the wave of organized land invasions in Montevideo around 1990. Using qualitative and quantitative analysis of squatting events over time, it argues that the rising electoral competition and the arrival of the leftist coalition Frente Amplio to the city government, constituted a key political opportunity for the urban poor.