The Reagan era or the Age of Reagan is a periodization of United States history used by historians and political observers to emphasize that the conservative "Reagan Revolution" led by President Ronald Reagan in domestic and foreign policy had a lasting impact. It overlaps with what political scientists call the Sixth Party System. Definitions of the Reagan era universally include the 1980s and the early 1990s, while more extensive definitions may also include the late 1970s, all of the 1990s, and even up until the late 2000s or the present. In his 2008 book, The Age of Reagan: A History, 1974–2008, historian and journalist Sean Wilentz argues that Reagan dominated this stretch of American history in the same way that Franklin D. Roosevelt and his New Deal legacy dominated the four preceding decades.