In the end, the decision to leave was Holder's alone — the two sources tell NPR the White House would have been happy to have him stay a full eight years and to avoid what could be a contentious nomination fight for his successor. Holder and President Obama discussed his departure several times and finalized things in a long meeting over Labor Day weekend at the White House.
The New Yorker's Jeffrey Toobin reported earlier this year that Holder planned to step down in 2014.
Holder's most recent appearance in the national spotlight was his visit to Ferguson, Missouri, during the protests that followed Michael Brown's killing; even before that, Slate's Jamelle Bouie wrote that one of Holder's roles in the Obama administration was to speak candidly about racial injustice in a way that the president did not feel politically comfortable doing himself.
NPR cites Solicitor General Don Verrilli as a potential Holder successor.