Social norms influence how opinions are expressed. The norm against prejudice discourages individuals from expressing certain opinions to avoid being perceived as prejudiced. This article examines recent empirical advances investigating the mechanisms of how this norm changes: how it is established and how it erodes. Recent research suggests that trigger events, such as elections, can abruptly change the norm. Factors such as group identification and a person's individual level of prejudice influence the impact of these events. At the individual level, exposure to violations of norms in the form of prejudiced comments or exposure to social sanctions can, respectively, weaken or strengthen the norm.