Abstract: Background Research shows that there is variation in how responsive individual politicians are to voter preferences. One explanation, it is commonly argued, lies in politicians' varying electoral motivations. Methods We test this assumption in a survey-embedded experiment in which Belgian Members of parliament were asked what position they would take on a policy proposal after a random half of them had been shown real survey data indicating that their party voters were in favor of this policy. Results We find that politicians who feel unsure about their re-election adapt their behavior more to be in line with the preferences of voters than confident politicians. Moreover, the anticipation of electoral accountability fosters responsiveness; the more politicians anticipate to be held accountable on Election Day for what they do and say, the more they respond to voter preferences. Conclusion These ideas are not new, yet we are the first to isolate them empirically and demonstrate their individual-level foundations.