While party membership figures are clearly in decline in several Western countries, different interpretations have been offered on the likely consequences of this trend. Some authors stress that members have lost most of their importance for political parties that increasingly rely on professionalized campaign techniques. Other scholars have expressed concern about the decline of party membership. They emphasize the fact that party members continue to function as an important linkage mechanism providing a structural alignment between the party and society (and thus also to potential voters). By means of an election forecasting model for Belgium, we test whether party membership figures can still be related to election results. Results show that party membership has a strong effect on election results and, furthermore, that this relation does not weaken during the period under investigation (1981–2010). The analysis also demonstrates that forecasting models can also be used in a complex multiparty system like that of Belgium.