I relied on the subjective group dynamics framework to analyse the derogation of inparty candidates involved in negative campaigns. In an experimental study (dynamic simulation of an electoral campaign, N = 118), I found that participants downgraded the inparty candidate (both in terms of evaluation and vote choice) more when he ran a person‐based negative campaign than when he ran an issue‐based negative campaign. This effect was significant for participants with high levels of political identification only. Overall, the findings revealed that political candidates, as members of significant social groups, are not exempt from the forms of extremity in evaluations typically observed in other social groups.