Electoral campaigns and policy debates are dynamic processes that unfold over time. In the contest for public opinion, each side tries to frame issues to its advantage, but success also depends on developing effective responses to opposition frames. Surprisingly, scholars have paid little attention to the dynamics of counterframing. In this article, we explore how the timing and repetition of counterframes affect their success. Using an over-time experiment, we test several hypotheses that the best counterframing strategy is contingent on the nature of audiences. Our results show that counterframing effects depend on the extent to which people hold strong or weak opinions. Thus, a uniformly successful communications strategy may be impossible as tactics that are effective on those with weak attitudes may be counterproductive on those with stronger viewpoints. We conclude with a discussion of normative and practical implications.