Habba is not the Acting U.S. Attorney for the District of New Jersey by virtue of her appointment as First Assistant U.S. Attorney because only the first assistant in place at the time the vacancy arises automatically assumes the functions and duties of the office under the FVRA. Additionally, because Habba was nominated for the vacant U.S. Attorney position, the FVRA's nomination bar prevents her from assuming the role of Acting U.S. Attorney.