Many historians have argued that the rise of television in the 1950s and the 1960s has had an enormous significance to the display and workings of politics. What is remarkable is that observations about the political importance of television often ignore the role of radio, as a medium which is closely affiliated to television, but which saw its breakthrough to a mass audience in the 1920s and the 1930s. Against this background this study explores the significance of radio to interwar political culture. It does so by comparing the political dealings with radio by two likeminded political parties, the SDAP in the Netherlands and the Labour Party in Great Britain. Both parties faced entirely different circumstances in broadcasting. While the SDAP was closely affiliated to the socialist broadcasting association VARA, the Labour Party found itself facing the mighty BBC. Yet, this study sees radio as a medium that was essentially the same in both countries, which meant that its rise raised a similar challenge for both parties to adjust their rhetoric and presentation to the medium-specific qualities of radio. As such, this comparison has not only highlighted a wide variety of differences between both parties, but also a number of unsuspected parallels. In fact, this study argues that these parallels offer vital new insights, not just to understand why radio has long been ignored by political historians and political scientists, but also to conclude that its political significance was really far greater than has been recognized so far.