The Movement Toward Socialism (MAS) emerged in Bolivia's Chapare region in the 1990s. Born of a rural social movement of coca growers, it spread to the cities and became the country's dominant political force as its leader, Evo Morales, was elected to the presidency in 2005. This article argues that the MAS is a hybrid organization whose electoral success has been contingent on the construction of a strong rural‐urban coalition, built on the basis of different linkages between the MAS and organized popular constituencies in rural and urban areas. Whereas the MAS's rural origins gave rise to grassroots control over the leadership, its expansion to urban areas has fostered the emergence of top‐down mobilization strategies. The analysis also reveals how much popular sectors allied with the MAS have pressured the Morales government from below and held it accountable to societal demands.