The concept of government can be used in two ways. In a broader sense, it may refer to the overall system of government and the relationships among the various institutional actors. Or, it may focus on the working of the executive branch. This matrix is an attempt to incorporate - and bridge - both approaches.

The vertical axis highlights the competition for governmental control. One key feature of presidential systems is the autonomy presidents enjoy with respect to both majority and opposition parties. On the other pole, party government relates to the leading role of political parties in forming cabinets and setting the governmental agenda. The horizontal axis refers to the basis of governmental legitimacy, whether through the legislature or directly from the people.

The LRQ is the quadrant of party government parexcellence, the Westminster model, where a party controls the executive thanks to its majority in the legislature, with a "fusion of powers" between the two branches, and effectively directs the policy-making process through a cohesive cabinet. A different regime of party government is depicted in the LLQ, where a PR electoral system protects minorities' representation and maximizes the search for consensus in the forming of coalition cabinets (Lijphart 1984). The URQ describes the classical U.S. system of separation of power, in which the governmental agenda often results from the aggregation of different political interests, through a process of legislative logrolling. Cespite their direct electoral mandate, presidents depend on congressional support to carry on their program, the more so when their party has no majority in either chamber and the resulting balance of power is one of "divided government" (Shugart and Carey 1992). In the last quadrant (ULQ) presidential government becomes fully presidentialized (Tulis 1987, Poguntke and Webb 2005). By reviving the popular mandate through permanent campaigning, presidents take full advantage of their direct relationship with the electorate asserting their leadership on the decision-making process. In the age of mass communication, this may lead to an emphasis on issues with a wide and dramatizing impact, whether in the international or national arena, often setting presidents' action loose from constitutional constraints (Lowi 1985). [Fortunato Musella]