 Prior to the establishment of the modern office of Lieutenant Governor following a constitutional referendum in 2005 that took effect in 2009, a vacancy in the office of governor would lead to the president of the state Senate to become acting governor while still retaining the title of senate president.Following the resignation of Christine Todd Whitman in 2001 to become EPA Administrator, Donald DiFrancesco assumed the acting governor's post, serving until January 2002.Following DiFrancesco's departure from the senate, John O. Bennett and Richard J. Codey each served as acting governor as well.