The American judiciary, like other branches of government, has increasingly come under attack as both ideologically driven and politicized. Using an original dataset that captures the ideological positioning of nearly half a million judges and lawyers who have made campaign contributions, we present empirical evidence showing politicization through various tiers of judicial hierarchy. Specifically, we show that, the higher the court, the more conservative and more polarized it becomes, in contrast with the broader population of attorneys, who tend to be liberal. These findings suggest that political actors not only rely on ideology in the selection of judges onto courts, but that they do so strategically, prioritizing higher courts. As explanation for these findings, we present a model of judicial politicization that formulates the ideological composition of the judiciary as a function of the ideological distributions of attorneys and politicians. To our knowledge, our study is the first to provide a direct ideological comparison across tiers of the judiciary and between judges and lawyers, and also the first to document how -- and why -- American courts are politicized.