Legacies of political violence and varying levels of tolerance toward such actions remain critical for understanding political attitudes in territories with a recent past of intense terrorism, like the Basque Country. However, measuring tolerance for political violence poses significant challenges, as respondents may provide socially desirable rather than truthful answers. This study pursues two primary objectives: (1) to assess the latent tolerance for political violence among Basque citizens, and (2) to estimate the extent of underreporting of these attitudes in survey responses. To address these goals, we employ a list experiment embedded within a survey of a representative sample of the Basque population (N = 2172). By comparing the results of the list experiment with those from a direct (intrusive) question (included in the same survey), we find that the overall acceptance of political violence for achieving political goals is approximately 10% when estimated with the list experiment—a figure 2.5 times higher than the estimate obtained through the direct question. Furthermore, we identify heterogenous patterns in the acceptance of political violence and susceptibility to social desirability bias, linked to respondents’ background characteristics.