Since Maurice Duverger’s (1954) seminal work, a large literature in political science has examined the effects of electoral rules on candidate and voter behavior, establishing a strong empirical relationship between the electoral system and the number of candidates (or parties) entering an election in each district. This literature, however, developed focusing primarily on established (mostly Western) democracies and, as a result, it is unclear whether these same electoral rules have similar consequences in authoritarian elections. Electoral rules are an important set of institutions even in the electoral authoritarian regimes of the Middle East and North Africa affecting electoral outcomes, representation, long-term institutional stability and democratic transitions (Lust-Okar and Jamal 2002; Posusney 2005; Herb 2005). Nevertheless, few systematic empirical studies exist examining the effects of electoral rules on candidate behavior in the Middle East and North Africa. This paper fills an important gap in the literature on the consequences of electoral systems in non-democratic settings. Using district-level data on the number of candidates competing in each election, this paper examines whether electoral rules in Jordan produce the expected reductive effects on the number of candidates competing in each electoral district. Upon first examination, there appears little evidence that elites are learning and entering races strategically. However, when candidates are grouped by tribal affiliation—an important social and political institution in Jordan—there is much more evidence of strategic behavior. Moreover, I find interesting variation across both electoral districts and tribes suggesting the effects of electoral rules in Jordan are conditional. To explain this variation across both districts and tribes, I employ a mixed-method research design. First, I use regression analysis to identify the correlates of the number of candidates running per seat in each district across election years. I find the effect of electoral rules to be conditional on ethnopolitical heterogeneity (measured by the proportion of Palestinians living in the district and the existence of minority quotas) and district size. Second, I use a structured comparison of electoral districts and tribes in Irbid, Kerak, Zarqa and Bedu Wasat. From elite interviews, conducted in June and July of 2012 with tribal leaders and candidates, the size of the tribe, socioeconomic changes and prestige emerge as important determinants of the number of persons from each tribe entering as candidates in a district.