In the United States, the nomination of the candidate for the two major parties falls to the citizenry as well as the major establishment parties. The two major ways that states decide on its nomination is through primaries and caucuses. A primary and caucus are both methods in which a state decides on a candidate for nominations.
The main difference between a primary and a caucus lies in the fact that a caucus only allows for members of the party to vote within a given state, which in turn decides the state's choice for a nominee. As such, it is only those identifying with the two large parties in the United States who are capable of casting a vote, although the two major political forces in the United States are broad enough to provide some platform for all of the population. Ideally, this would not be a massive inhibition in a vote being representative of the people, but the reality is that in the United States, the two parties are not entirely representative of the population. In practice, the United States should have a representative democracy that truly allows for full representation of its voting population, but that simply is not the case. If anything, the use of caucuses guarantee that the United States cannot effectively represent its population.
The problematic issue of the caucus is it leads to inherently misrepresentative results in a democracy. In the United States, an astounding 43% of the population is registered as independent. Assuming that such a figure is equally distributed across the United States, this implies that half of the American population in states with a closed primary or caucus is not capable of voting in a preliminary election to decide the future of the United States. The end result severely skewers the representation of the state's population. In addition, recent studies support the perspective that those voting in caucuses are also likely to hold more assertive beliefs, which can cause politics to become more extreme in the process, due to the fact that only committed party members are those who vote in caucuses.
Though one can make the argument that the use of caucuses is sporadic in the United States, the fact of the matter is that the nature of American elections have also provided a large amount of disillusionment in political participation, which has only compounded the misrepresentation that comes from the flawed political system. The remedy to such misrepresentation and bipolarity would be in theory to open participation to all citizens regardless of registered dispositions.