No incumbent who served his full term in Gallup poll history has ever won re-election when he was not leading by atleast 9 points by September since Roosevelt in 1946 when he only lead by two. Thats 6 out of 7 full term incumbents who had a 9 point lead or more by this time who have won. The three who didnt have lost. Bush is now only tied. Remember back then they did not use likely voters only registered.
Caviat-Truman was down in 1948, but he took over after the death of Roosevelt. Gallup called that race for Dewey(Dewey lead in Sept was by 9). Well we know what happened there.
Caviat-Ford also was not a full term president.
INCUMBENT WINNERS-
1940-Roosevelt lead by 9.(Roosevelt won)
1944-Roosevelt lead by 2.)Roosevelt won)
1956-Eisenhower lead by 11. (Eisenhower won)
1964-Johnson lead by 30.(Johnson won)
1972-Nixon lead by 28 points.(Nixon won)
1984-Reagan lead by 21.(Reagan won)
1996-Clinton lead by 21.(Clinton won)
INCUMBENT LOSERS-
1980-Carter lead Reagan 44-40(Carter lost)
1976-Carter lead Ford 47-45 (Ford lost)(not a full term incumbent)
1992-Clinton lead Bush by 9 (bush lost)
2004-Bush and Kerry tied 47-48 (?????)
http://www.gallup.com/content/default.aspx?ci=1252 http://www.gallup.com/content/default.aspx?ci=1255 http://www.gallup.com/content/default.aspx?ci=1249 http://www.gallup.com/content/default.aspx?ci=1252 http://www.gallup.com/content/default.aspx?ci=1246 http://www.gallup.com/content/default.aspx?ci=1237 http://www.gallup.com/content/default.aspx?ci=1234