The departure of U.S. Attorney General Eric Holder deprives the Obama administration of a powerful voice on civil rights at a time when riots in Ferguson, Missouri, have thrust the issue into the spotlight.

Civil rights advocates fear his exit leaves a hard-to-fill hole on Obama's team when it comes to events such as in Ferguson — where days of protests followed the fatal police shooting of an unarmed black teenager — and challenging laws in some states requiring voters to show photo identification, measures that Holder has said would prevent black and Latino voters from going to the polls.

They are worried that his work on voting rights, sentencing reform, and addressing racial profiling measures used by police could fall by the wayside when his yet-to-be-determined successor sets a new set of priorities — particularly as the administration focuses on counterterrorism and the threat posed by militants from the Islamic State group.