Broadly speaking, social movement scholarship has proceeded in three waves. The first wave of scholarship explored the reasons why people engaged in protest, and developed approaches steeped in psychology and social psychology. The second wave sought to explain the conditions in which collective action is most likely to take root and bear fruit. These approaches emphasize micro- and macro-level processes key to the generation of insurgency: war, economic change, organizational strength, the mobilization of resources, and culture. The most recent wave aims to assess movement outcomes, perhaps the most important of which are adjustments to public policy. The Political Power of Protest fits squarely into the aforementioned niche.

In this book, Daniel Gillion asks a simple yet important question: Is protest on the part of minorities a viable means for them to finally achieve the benefits of first-class citizenship—by way of public policy—long promised by the American creed? This question may come as a surprise to some, but the jury is still out on whether or not protest ultimately gives way to changes in public policy. Gillion proposes a novel theoretical approach, coupled with an impressive array of evidence, to test his contention that protests on the part of minorities matter. In the end, he finds that protest—above and beyond competing explanations—is important.

To tap what he calls “The Influence of Minority Political Protest,” the author constructs a “continuum of information,” his theoretical lodestar. To do this, he builds on well-known signaling theory in which political actors may both send and receive signals: as a means of informing interested parties of their intentions, in the case of the former, or as a means of divining the intent of other parties, in the latter case. In the book, Gillion draws on the latter use of signaling, applying it to the ways in which individuals situated in the three branches of government react to the signals emitted by minority protest. The information continuum runs from the “low salience” condition, in which the signal sent by protests is not “informative,” to the “high salience” condition, in which protests are perceived as “more informative.”

What determines the placement of a given protest on the information continuum? The size of the protest, in the absence of other factors, does not matter. As a result, it provides relatively little information. But if a protest is accompanied by persistence over time, violence, police presence, and strong organizational support, it sends a relatively strong signal. Gillion’s argument is that members of the national legislature (i.e., Congress), the Executive, and the Supreme Court, assess the intensity of the signal sent by protest, and attempt to adjust policy based upon the “strength” of the signal. The more intense the signal the movement is able to generate, the more likely a given branch of government is to act.

This finding is a welcome addition to the burgeoning literature on the protest—policy nexus. I particularly like the way in which Gillion applies signaling theory to movement—countermovement dynamics, something that requires him to account for the competing signals that public officials must consider. Theorizing and measuring this innovation requires originality; also, the methods are first rate. Further, I remain fascinated with the effect of protest on the Supreme Court. It is far easier to understand why the executive and legislative branches may yield to protest tactics: The respective occupants must worry about the next election. But with lifetime appointments, Supreme Court justices face no such pressure. Still, the results suggest that minority protest managed to influence how the Court ruled on minority-related cases during the Civil Rights movement.

I am convinced of the findings presented in the book. However, like most (honest) book reviews, my positive appraisal comes with some caveats, all of which are tied to the analysis.

I found Gillion’s interpretation of the findings understated, even a bit underdeveloped in some cases. For instance, in his analysis of the effect of protest on the House, Gillion notes that “protest levels … decreased the number of minority hearings.” He goes on to say that the “results are quite sobering,” presumptively because they run counter to his theory. But he adds that these results are in keeping with prior work in that “collective minority protests are not influencing a unified response from Congress” (p. 69). First, a better explanation is required if the results run in the opposite direction of the theoretical prediction. Second, as far as I know, prior work does not find that protest actually dampens support for legislative action. Rather, these works find no effect at all—positive or negative—accruing to protest. That is a far cry from Gillion’s results, ones that track in the opposite direction from what his theory predicts. Another caveat rests on the selective use of a product term in which public opinion is hypothesized to moderate the effect of protest on Supreme Court decisions. While the effect is small, it remains significant. Such a specification, to my mind, could have been put to good use elsewhere. Why is the effect of protest contingent upon public opinion where the Court is concerned, but not elsewhere?

Caveats aside, from theory to method, this is nice piece of social science, one with which political scientists and social movement scholars must reckon if they wish to come to a full understanding of the true political power of protest.