Under what conditions do intricate pre-planned arguments enable negotiators to dominate the conversation and ultimately the outcome? We proposed the advantage occurs when the communication media involves the expectation of rapid turn-taking, because counterparts cannot generate rebuttals in time and end up making concessions. In an experiment with a negotiation task, sellers were provided with either intricate or simple arguments to support a competitive tactic and negotiated via either a quick-tempo (Instant Messaging) or slow-tempo (E-mail) medium. As predicted, intricate (versus simple) arguments enabled sellers to claim more value in the quick (Instant Messaging) but not the slow (E-mail) medium. Mediational analyses traced this effect through two process measures: the extent to which sellers enacted the competitive strategy (coded from transcripts), and the extent to which buyers consequently felt "at a loss" (measured by self-reports). We discuss the theoretical and practical consequences of these findings for negotiations.