Patrick A. Nash was a political boss in the early and mid-twentieth century in Chicago and Cook County. He was in large part responsible for consolidating elements of the Cook County Democratic Party into a political machine. He evolved from a local sewage contractor to a political boss by carefully selecting his political allies. His prominence stems from the death of Anton Cermak and his political career is intertwined with that of Edward Joseph Kelly. The success of this machine was attributed to its decision to be more inclusive than its predecessors. This meant that Nash had success at dealing with a variety of politicians such as William L. Dawson.

The Cook County Democratic Party is an American county-level political party organization which represents voters in 50 wards in the city of Chicago and 30 suburban townships of Cook County. The organization has dominated Chicago politics since the 1930s. It relies on an organizational structure of a ward or township committeeperson to elect candidates. At the height of its influence under Richard J. Daley in the 1960s when political patronage in employment was endemic in American cities, it was one of the most powerful political machines in American history. By the beginning of the 21st century the party had largely ceased to function as a machine due to the legal dismantling of the patronage system under the Shakman Decrees issued by the federal court in Chicago. The current Chair is Toni Preckwinkle, who is also the elected Cook County Board president.