The key element of political life in the Medieval period was feudalism. This meant that politics during this time was a very personal affair based on personal loyalties rather than on loyalty to a country or to a political system.
In feudalism, politics was a personal affair. A vassal did not feel allegiance to the country of England (for example) or to the government of England as an entity. Instead, that vassal felt allegiance to his lord. He felt this allegiance because of personal vows exchanged between the two of them.
Thus, the key element of political life in Medieval times was the bond that was made between lord and vassal in the feudal system.