"Her support gave our movement for more and better research a critical boost right from the start. We are thrilled that she is returning to mark our 15th anniversary and the progress she helped make possible," Axelrod said in a statement.

Clinton, the odds-on favorite for the 2016 presidential nomination were she to decide to run, has slowly begun to reemerge into public life since her retirement from the State Department earlier this year. Last week, she began a series of paid speaking appearances with an event in Dallas, where she earned a reported $200,000.