We develop a model where party leaders choose the competence of politicians on the ballot to trade off electoral success against their own survival. The predicted correlation between the competence of party leaders and followers is strongly supported in Swedish data. We use a novel approach, based on register data for the earnings of the whole population, to measure the competence of all politicians in 7 parties, 290 municipalities, and 10 elections (for the period 1982-2014). We ask how competence was affected by a zipper quota, requiring local parties to alternate men and women on the ballot, implemented by the Social Democratic Party in 1993. Far from being at odds with meritocracy, this quota raised the competence of male politicians where it raised female representation the most. We argue that resignation of mediocre male leaders was a key driver of this effect.