Landslides: 1864, 1872, 1900, 1904, 1924, 1956, 1972, 1984
Non-landslide: 2004
An error once again. You can factor out 1904 and 1924, when there was no previously elected incumbent. In 1964, the was
no South, voting in the Presidential election at least.
The only comparable ones are 1872, 1900, 1952, and 1972. In 1900 McKinley increased his percentage of the popular vote by about 0.5%. In 1872, Grant had slightly under 3% increase. Eisenhower only had a 2.5% increase. Only Nixon and Reagan had a greater increase in their share of the PV.
Even when compared to Ike, Bush's popularity with the electorate has grown.