I investigate how radical right candidates affect voters' choice to cast a ballot and (if so) which party to support, and the decisions by other parties to field a candidate. To approach these questions, I use a Regression Discontinuity Design exploiting the fact that, in France, the first-round vote share discontinuously determines who advances to the second round of the election. I find that the presence of a radical right candidate in the second round raises turnout rates. The decomposition at the precinct level suggests that the main driver of the boost in turnout rates comes from loyal radical right voters who only vote when their favorite candidate runs. The effects are stronger when the radical right's expected probability of winning is high and when political polarization is high. In addition to the effect on turnout, I also find that left-wing parties respond by coordinating more often on a single candidate. The presence of radical right candidates hence affects both voter and party behavior and thereby changes the electoral dynamics and ultimately who is elected. When the radical right candidate is ranked third or lower, the vote share of conventional right-wing candidates decreases more than for conventional left-wing candidates, which results in a lower probability of winning for the conventional right. When the radical right candidate instead is the runner-up, the top conventional candidate is almost certain to win, which is not the case when the top runner's main competition comes from another conventional candidate.