Head of State

• In parliamentary systems, the head of state is usually a monarch who serves as the ceremonial representative to other countries and gives final consent to laws generated by parliament. It is actually the prime minister who serves as head of government and leads the day-to-day activities of government in the parliamentary system. On the other hand, the president in a presidential system fulfills the roles of both the head of government and the head of state.
  
  

Election of the Chief Executive

• In parliamentary systems the head of government, the prime minister, is a member of parliament elected by other members of parliament. This characteristic means that the prime minister is responsible to the other members of parliament and through them, the voters. The presidential system is different in that the president is directly elected by the people and thus directly responsible to them. In the U.S. the president must work with Congress to run the government but Congress does not have the power to vote him into his position or remove him through a vote of no confidence as in the parliamentary system.
  
  

Coalition Formation

• Due to the nature of parliamentary systems, if a political party does not win a clear majority of seats then the leader of the party with the most seats must work to form a coalition with other parties. If the prime minister (as head of the dominant party) is not successful or at some future point the coalition ceases to be a majority, then the government collapses, meaning a new prime minister is elected and a new coalition formed.
  
  In presidential systems there are no formal systems of coalition or cooperation. Political parties may work with one another on any issue but the party makeup of the legislative body does not impact whether the government can function.
  
  

Party Discipline

• Party discipline is the degree to which individual politicians vote in line with the agenda of their declared political party. Generally, members of parliamentary systems tend to exercise much more party discipline than their counterparts in presidential systems. This is because in a parliamentary system, the executive and legislative functions are somewhat fused and there is more pressure exerted on each member of parliament to stay in line. On the other hand, in presidential systems like the U.S., it is not at all uncommon for congressmen to "defect" from their party on a issue that has special meaning to them.