In the last decade, studies have documented how autocrats use elections as a way of legitimising and stabilising their regimes. Simultaneously, a literature on negative external actors (also known as ‘black knights’) has developed, emphasising how various international actors use anti‐democracy promotion strategies to undergird authoritarian regimes. In this article, these two literatures are fused in an attempt to shed light on the external dimension of authoritarian elections and what is termed ‘black knight election bolstering’. First, five mechanisms are elucidated, through which external assistance increases the chances of ‘winning’ elections in authoritarian settings (signaling invincibility, deterring elite defection, undermining opposition activities, dealing with popular protests, and countervailing pressure from foreign democracy promoters). Second, it is argued that external actors are most likely to offer election bolstering when they face a particularly acquiescent partner or when electoral defeat is perceived to lead to radical and undesired regime change. The relevance of both factors is augmented when uncertainty of the electoral outcome is high. Finally, four cases of Russian intervention during elections in three authoritarian neighbour countries (Ukraine in 2004, Belarus in 2006, and Moldova in 2005 and 2009) are analysed. The case studies corroborate the theoretical arguments: not only does Russia engage in all five types of black knight election bolstering, but it does so only when one or more of the three explanatory factors are present.