Why do social movements occur? All the keys to understanding both their success and their failure

For some authors, social movements occur when a group of individuals, dissatisfied with government policies, organize collective action, in order to:

• To attractively defend a cause
• To gain the adherence of a group of activists
• To gain public attention

Social movements, unlike political parties, do not seek to gain power. Thus, social movements aim to influence societal values to change them in the direction they advocate.Historically, social movements have emerged, above all, in the 50s, 60s, and 70s (the civil rights movement in the US, feminist movements, environmental movements...). And one of the main characteristics of social movements is that they consider usual methods of social protest ineffective, so they seek forms of high public impact (demonstrations, strikes...). The use of these forms are characteristics that distance them from other actors such as political parties

The Political Opportunity Structure: Sidney Tarrow's Theory

For his part, and also from a political perspective, Sidney Tarrow focuses his analysis on the conditions of opportunity in which mobilization takes place. Collective action, as a political phenomenon, is determined by a set of constraints and opportunities that influence it, giving it a concrete form. This is what gives rise to the concept of political opportunity structure (POS).

The success of a movement does not depend exclusively on the degree of frustration in a society, nor on the ability of political entrepreneurs (McCarty and Zald) to generate mobilization, but rather on the existence of a structure of opportunities that enables its emergence and subsequent consolidation (that is, that it can endure over time).

Social movements are therefore understood as organized structures that occasionally succeed, depending on a political opportunity structure and not as the result of the degree of frustration in a societyAccording to Tarrow, the movement will succeed not only because of its structure but also because of how it knows how to leverage external resources. The EOP concept emphasizes resources "external" to the group (there are external political opportunities, for example). Context also matters

Tarrow therefore defines collective action, as a political phenomenon, as determined by a set of constraints and opportunities that influence it, giving it a concrete form—which will give rise to the concept of political opportunity structure (POS). Tarrow tells us that a social movement does not depend solely on individual frustration. He understands that there are other elements that explain the emergence and consolidation of social movements.

There are external resources that influence the emergence and consolidation of social movements. By external resources, we refer to the social and even political context that surrounds the social movement.

Tarrow therefore understands social movements as organized structures that occasionally succeed, depending on a political opportunity structure and not as the result of a society's level of frustration

The Necessary Conditions for a Social Movement to Succeed

Tarrow points to four (now five, since the publication of his work Strangers at the Gate in 2012) dimensions of the Political Process Opportunity Structure (POS):

1. The degree of openness presented by political institutions: structural and conjunctural factors of the political system. Potential of institutional structures to allow for mobilization —depending on the political structures of each country, social movements will be able to make their way in one form or another.
2. The instability of political alignments: the existence of electoral instability favors collective action. Starting from the conception of collective action as organized action, which shows a connection of interdependence with institutional political action, whose variations have repercussions on the former (institutional political action has repercussions on collective action).
3. The presence of allies and support groups: movements are connected with parties or pressure groups as support structures that enable institutional access for organizations that would otherwise not have it —support groups facilitate the entry of social movements themselves into the institutional channel.
4. Divisions within the elite or their tolerance or intolerance towards protest: conflicts among elites, division among them favors the success of mobilization —when Tarrow speaks of elites, he normally refers to the political class and those actors who play a fundamental role in the functioning of the system. The success of mobilizations also influences the success of social movements so that they can break into the system.
5. The existence of repression: for some scholars, repression is an obstacle to mobilization, while for others, like Tarrow, repression angers the population and increases the size and scope of mobilization. It is possible that the effectiveness and not the degree of repression is what causes mobilization.

The structure of political opportunity influences the chances of success for movements, but furthermore, for Tarrow, one must also consider the importance of political cycles, the existence of periods of general mobilization, the set of resources, and the constraints that characterize each cycle. By political cycles, Tarrow refers to the political conjuncture that can make a social movement succeed or fail—some cycles are more favorable to social mobilization than others

The concept of EOP helps us understand, for example, why social movements sometimes acquire a surprising, though at times transient, capacity to pressure elites or authorities and then quickly lose it despite all their efforts.

Neither the most favorable political opportunity structure nor the most efficient organization are capable of ensuring the success of social movements. This is where the idea of political cycles comes from, that is, the existence of certain periods of general mobilization.

Political action, therefore, for Tarrow, must be analyzed taking into account the set of resources and constraints that characterize each social cycle, since the components of the political opportunity structure depend largely on these cycles

In this regard, several of Tilly's works found that mobilization peaks in 1830s France were more related to electoral opportunities and regime changes than to deprivations and difficulties themselves (Tilly, 1978). However, Tilly never got around to talking about political cycles.