This article aims at an empirical verification of prosecutors' partisan behavior through a case study based on the Russian President Yeltsin and Putin periods. According to Gretchen Helmke's original theory of strategic defection, dependent judges may occasionally check their principal, the executive leadership, by withdrawing their support in the course of an electoral cycle. However, a modified theory of strategic defection can be readily applied to civil-law prosecutors' behavior in new presidential democracies, where several presidents dominated that office during most of their tenure but experienced prosecutorial defection in their final phase. Russia provides a textbook case for examining the modified theory in relation to prosecutors' partisan behavior against an incumbent president. Meanwhile, this paper uses within-case analysis based on a qualitative method, because the methodological approach can have more advantages in discovering whether prosecutors acted really' strategically when an incumbent government was outgoing in Russia, and in further explaining a pattern of prosecutors' partisan attitudes in new presidential democracies, through the modified version of Helmke's theory.