This article studies the political trajectory of the Chilean middle class under the Popular Unity government (1970–1973) through its representative social organizations, especially small merchant, trucker owner, and professional associations. In the context of increased political polarization, the middle class—after a brief “honeymoon” with the government—radicalized for counterrevolution. Along with political, media, and business opposition, these middle-class groups formed a powerful counterrevolutionary social bloc that challenged the Popular Unity through massive strikes and protests, including a major one in October 1972. I argue that this process was a result of the breakdown of the channels of participation and negotiation that had existed between these groups and the state since the 1930s. These channels broke down with the Left’s implementation of a revolutionary, socialist project, which led both to the state’s unprecedented attention to the working class and to a major economic crisis. At the same time, the very idea of the middle class was redefined in counterrevolutionary terms. While the internal contradiction of the Left prevented it from engaging with the middle class, the opposition succeeded in defining that social identity as inherently anti-Marxist. Consequently, the organizations studied here assumed a leading role in the increasingly insurrectional opposition to the Popular Unity, which culminated in enthusiastic middle-class support for the September 11, 1973, coup d’état.