After four gruelling months of personal combat, 45 different primaries, caucuses and state conventions (leaving nine to come), and tens of millions of dollars spent on television advertisements (with many more expensive commercials yet to be aired), the voters of Pennsylvania have finally managed to define what it is that is at the core of the contest between Hillary Clinton and Barack Obama. It is essentially cultural and not political. It is a struggle between The Waltons and The Cosby Show.

Mrs Clinton's electorate consists of those who empathise with the Walton clan of the 1970s. Her appeal is to white working class (and some middle class) Americans who have to struggle to make ends meet, who expect the government to attempt to ease those burdens, whose lives revolve around family and faith and who tend to be socially conservative at the same time as they might be categorised as economic liberals. They are instinctive Democrats, but if the party moves too far to the left of them they bolt to an Eisenhower, a Nixon, a Reagan (especially), or a Bush.

Meanwhile, the exit polls imply, Mr Obama's base support overlaps with those who adored the Huxtables in The Cosby Show, which dominated US airwaves in the 1980s. That programme attracted African-Americans, affluent whites and viewers under the age of 30. It was an uplifting tale of achievement and reconciliation. Some critics asked, though, if it reflected the real world.

John Edwards, who long ago disappeared from this struggle, spoke constantly about “two Americas”. He was right but may be surprised to find that they both exist inside the Democratic Party.