"Rebuilding the party will take time. While it isn't an easy task, we developed a strategy, we implemented it, and we won races up and down the ballot in 2017," O'Connell said in a statement to NBC. "While I've made the decision to pass the baton, our work remains far from over and under Tom Perez's leadership and direction, our party will continue to build on the progress we've made in 2017," O'Connell continued.