The West Wing
In general, The West Wing attempts to create an alternative reality, in which there is a subtly different set of historical truths in the 1970s, 1980s and 1990s. In particular, the show tries to suggest that the last "real" president in its timeline is Richard Nixon, and to chart the careers of its principal players in the light of that decision.  Nevertheless, there are occasions in which more contemporary presidents are implied.