How do partisan campaigns influence voting behavior in high salience elections? In 2016, I conducted a field experiment in the German state of Baden-W\"urttemberg to evaluate the effectiveness of direct mail sent out by the Green party in a high salience election. I use a matched-pair randomized design to test the effects of a partisan valence direct mail treatment. Assessing the results with design-based methods of statistical inference, I find no effect of the letters on either turnout or vote choice. Nevertheless, this null result has important implications. First, political campaigns using direct mail as described in this study can save significant amounts of money. Second, this study shows that further experimental research within partisan campaigns is needed to better understand the effects of real campaign tools, especially in multi-party systems and high-salience elections.