The purpose of this paper is to investigate the relevance of 'switching costs' to the problem of terrorism and grassroots support of terrorism. Grassroots supporters that choose between the terrorist organisation and the government may face considerable costs in switching their support after their initial decision has been made. This paper presents an analysis of competition between the terrorist organisation and the government for grassroots support within a two-period economic setting. If grassroots supporters face costs, which may be either tangible or psychological costs, in switching to the government if they initially supported the terrorist organisation (and vice versa), economic theory produces results that have important policy implications. Of most importance, it can be shown that when grassroots supporters have switching costs there is more intense competition between the terrorist organisation and the government for grassroots support. Also, when grassroots supporters have switching costs, the terrorist organisation and the government must invoke more extreme measures in order to win supporters away from the other party.