Chapter 1 lays the groundwork for developing my theory of the gendered qualification gap and the empirical tests I conduct in later chapters. I start by defining the gendered qualification gap. The gendered qualification gap explains the empirical phenomenon where female candidates are just as likely to win their elections as male candidates but win by smaller margins and run in more competitive races. This empirical outcome is taken by some scholars and political pundits to mean that there is no consequential bias in voter decision-making. Yet these successful women have better qualifications than their equally successful male counterparts. This means that highly qualified female candidates are just as likely to win their elections as less qualified male candidates. If there were no gender bias in voter decision-making, then female candidates would be more likely to win their elections compared with less qualified male candidates. This chapter discusses how current explanations overlook the role that gender bias plays in how voters evaluate candidate qualifications. Past research examines how institutional barriers and socialization patterns contribute to the gendered qualification gap, but missing from the extant body of scholarship is how voters contribute to the qualification gap.