Social media plays an increasing role in mobilizing protest action. We examine the dynamics of how messages about the 2013 Million People March Protest in the Philippines propagated through Twitter. We identify two factors that affect the dynamics of the spread of protest message. First, we find evidence of social contagion in the form of a user’s recruitment threshold as certain users activate when a certain proportion of users they follow have already activated.

The recruitment threshold influences the timing of a user’s recruitment into the online movement as high threshold users spread the messages much later than low threshold users. Second, we found that a user’s k-core centrality affects the extent of the spread of the message. The most central users spread messages the farthest on the average. These findings shed light on the connection between the properties of an online social network, social contagion, and the dynamics of the spread of protest messages online.