Populist parties are often conceived of as ‘mobilizers of discontent’. They either attract voters who are dissatisfied with the political status-quo, or they fuel discontent among those who support them already. In this paper we argue and demonstrate that populist parties stop being mobilizers of discontent when they are in power. Based on three different studies, employing both cross-sectional and panel data, we show that the association between political discontent and populist support is contingent on whether a populist party is in office or not. We demonstrate that the discontent-populism linkage evaporates when a populist party enters a government coalition, and resurfaces again when it leaves office. In additional analyses of support-switching patterns and individual-level attitudinal changes, we explore the mechanisms underlying these patterns. Although our findings indicate that, as mobilizers of discontent, populist parties are tainted by office, our study also suggests that ‘office stains’ can be washed off relatively easily.