The impressiveness of this gap is underscored by looking at historical approval ratings for other presidents who were similarly gearing up for a re-election bid. Aside from Bush, Bill Clinton had the largest partisan gap in approval ratings at a comparable point in his presidency, but his 60-point gap from May 1996 is nearly 25% smaller than Bush's. Ronald Reagan is the only other president to have a partisan gap in excess of 50 percentage points in May of his re-election year.
Bush's 70+-point gap is not only unprecedented for May of a re-election year, but it is unprecedented for any point in a re-election year. No president, dating back to Harry Truman, has had a partisan gap above 70 points in any Gallup Poll in a re-election year.