"It is unfortunate that someone who is a non-partisan non-politician could not overcome the increasingly partisan tendencies of the state, even for an office that by its nature necessitates a non-partisan approach," Cooley said in a statement.
The race for the state's top lawman has been one of the closest statewide races in California history. Less than one percent of the votes separated Cooley from his opponent.
Harris led Cooley in the latest statewide vote count by 53,000 votes, and it was estimated that Cooley would need about two-thirds of the remaining votes to win. Those were in counties which Harris carried on Nov. 2.
Cooley prematurely declared victory on the night of Election Day, and then didn't show up for his own concession announcement.
Cooley's campaign had called a telephone conference to talk to reporters from around the state, but Cooley was never on the call. He left it to Spillane to make the concession announcement.
The San Francisco district attorney becomes the first woman and first minority elected as California's attorney general.
Harris issued a statement saying she will wait until all the votes are counted before she makes a public declaration.
"District Attorney Harris thanks District Attorney Cooley for a spirited campaign and looks forward to working together on the critical public safety challenges facing California," the statement also read.
Harris said she planned to hold a press conference on Nov. 30, the day the final vote counts are due for counties.