Attention to the American carceral state has focused largely on its bookends: policing and sentencing. Between these bookends lies an underresearched but far-reaching “shadow” carceral state, a hybrid of criminal and commercial systems that often contravenes the principles of liberty, due process, and equal protection. Pretrial detention is an iconic example. It accounts for the majority of people in local jails on a given day. Up to half of detainees will not be convicted, yet detention often lasts months and triggers significant losses. Most are detained because they are too poor to pay bail, and they are disproportionately Black. How does this widespread punitive, arbitrary, and unequal experience affect political behavior? Using administrative records and as-if random assignment of bail magistrates, we find that pretrial incarceration substantially decreases voting among Black Americans. These results point to the neglected but important shadow carceral state.