The European Council included a free and democratic Europe on its strategic agenda for 2024-2029. However, the success of several populist parties is a serious threat to achieving this goal. Understanding how mainstream politicians respond to this pressure can reveal shifts in the broader democratic discourse. Focusing on French parliamentary elections between 1958 and 2024, for which there are individual candidate manifestos, this paper will be the first to credibly show how political candidates strategically adjust their campaigns to populist opponents. The paper uses natural language processing methods to study the adjustment in three dimensions: policy topics, their rhetorical complexity, and the level of populism. Leveraging regression discontinuity designs and exploiting two-stage elections and the quasi-random presence of a populist candidate in the second round, the paper will show the causal effect of populist candidates on mainstream ones. The paper will also provide for the first time evidence of whether this adjustment is constrained to the political campaign or impacts the legislative activity of elected politicians by analysing their policy topics, the complexity of their legislation, and the level of populism in their debates.