  Increasing levels of far-right extremist violence have generated public
concern about the spread of radicalization in the United States. Previous
research suggests that radicalized individuals are destabilized by various
environmental (or endemic) factors, exposed to extremist ideology, and
subsequently reinforced by members of their community. As such, the spread of
radicalization may proceed through a social contagion process, in which
extremist ideologies behave like complex contagions that require multiple
exposures for adoption. In this study, I applied an epidemiological method
called two-component spatio-temporal intensity modeling to data from 416
far-right extremists exposed in the United States between 2005 and 2017. The
results indicate that patterns of far-right radicalization in the United States
are consistent with a complex contagion process, in which reinforcement is
required for transmission. Both social media usage and group membership enhance
the spread of extremist ideology, suggesting that online and physical
organizing remain primary recruitment tools of the far-right movement.
Additionally, I identified several endemic factors, such as poverty, that
increase the probability of radicalization in particular regions. Future
research should investigate how specific interventions, such as online
counter-narratives to battle propaganda, may be effectively implemented to
mitigate the spread of far-right extremism in the United States.
