Eisenhower/Obama overlay.
gray -- did not vote in 1952 or 1956
white -- Eisenhower twice, Obama twice
deep blue -- Republican all four elections
light blue -- Republican all but 2012 (I assume that greater Omaha went for Ike twice)
light green -- Eisenhower once, Stevenson once, Obama never
dark green -- Stevenson twice, Obama never
pink -- Stevenson twice, Obama once
No state voted Democratic all four times, so no state is in deep red.
Do you not believe me? Jimmy Carter's one narrow win depended upon getting all but one of the former Secessionist states. Obama won lots of Ford states.
Carter 1976, Obama 2008/2012
Carter 1976, Obama twice red
Carter 1976, Obama once pink
Carter 1976, Obama never yellow
Ford 1976, Obama twice white
Ford 1976, Obama once light blue
Ford 1976, Obama never blue