Australia's main parties have experienced rapid deterioration in levels of membership but most have been reluctant to follow the lead of many of their counterparts in Western Europe and embrace more radical, inclusive pre-selection formats to arrest declining numbers. This paper offers a partial explanation of why the Liberal and Labor parties have been disinclined to look to reforming candidate selection as a strategy to combat their shrinking rank-and-file membership. It argues that compulsory voting in conjunction with high levels of party identification has reduced the imperative for Australia's major parties to resort to candidate selection reform as a device to stabilise their voter base. This study underscores the important role of the institutional setting in affecting the incentives for parties to use pre-selection reform to combat a shrinking membership base.