Split-ticket voting in presidential and congressional elections of the United States

American people sometimes vote for candidates in opposite parties in presidential and congressional elections. Split-ticket voting is a kind of tactical voting in which a voter supports a candidate different to his sincere party preference. Actually the voter misrepresents his favored one or party to gain more desirable result and to prevent an undesirable outcome. This phenomenon is important in American election system. When people vote for one president of one party and a member of congress from another party, it is difficult to formulate distinct platforms for parties and it decreases the future certain assurance among people and parties. It is said about the American people that their behaviors are simple and uncomplicated, but there is a complexity in their voting behaviors.
The question is why the split-ticket phenomenon happens and what motivates the people to perform it?
The key answer is within the American system and people's trust to this system. National policy and interests for the US people and politicians have been the same for a long time and not much different to what the Americans Founding Fathers desired, but their levels have change due to different issues. They are always concerned with economic well-being, political values and security inside and outside of the country to preserve the US individual and universal prosperity. The terms right to life, liberty and the pursuit of happiness must be provided with a government that is devised to protect them all. It is done through controlling power with Constitution and the system of checks and balances between the federal executive, legislature and judiciary and between the senate and the House of Representatives and also between federal and state sovereignty. The process of lawmaking and popular elections are the safeguards of the system.
American people believe in the system which is at their service and just the way the services are provided are different. Through the American system individuals are unique, precious and important and they know the two major parties are the ones which provide what is needed for a desirable American life. Among the American presidents more than 20 were in office along with majority of opposition party members in the congress. There are different approaches and theories describing the causes and reasons of this phenomenon; some of them are offered here, but the conditions under which split-ticket happens, time and places before and after elections must be considered for all reasons.
1. According to 'Policy Balancing-Model' voters want to balance the relative policy extremism of the Democrat and the Republican parties. It also balances the government policies. For example, foreign affairs and the much to deal with them are important as far as considering the American people's rights, liberties, and the prosperity of American economic system. Partisan control is effective if majority of voters decide one certain thing to happen. So, there will be a balance not letting one party goes far.
2. Political observers sometimes thought that the electorate was not able to distinguish major and significant differences between parties. Some are not knowledgeable or well-informed to vote during the elections or they are more influenced by their families, friends, electoral campaigns or communities to make a different party choice.
3. American individualism influences decision making whether by policy makers or people. Parties are important as far as they provide what people want. Expectations of the American life are provided within either of the two major parties and that is why there is not a third major party. It happens that expectations are more important than the party identifications and reliable ness and whoever assures the electorates' hopes and anticipations to happen as hoped will be the right candidate to be chosen whether as the president or a congress person and despite his party affiliation. Party identification is not strong and the voter is not a whole supporter of either party.
Congressional elections take place in the mean time of president's term in office. So if one is not satisfied with what president promised to do, he easily shifts to choose someone from oppositional party to serve in the Congress or vice versa.
4. There is a theory that a great deal of split-ticket balloting and particularly in more recent elections are caused by the parties' increased ideological estrangement which differs between parties or voters.
5. Sometimes electorates vote against the president's party in off-year House elections as a kind of lagged split-ticket behavior to moderate the White House programs and or projects.
6. One theory is that this phenomenon is the result of different median policy positions of voters in nation-wide elections.
7. It happens most likely in ideological moderate districts which are typical of the party that represents them.
8. It sometimes happens with the lack of interactive differences as well as huge personal popularity of a certain candidate, like what happened in Eisenhower's time and went beyond partisan loyalties.
At the end it must not neglected that there are many that even do not make an effort to vote or vote just to have an impact on the election.

References:
http://en.wikipedia.org/wiki/Split-ticket_votinghttp://www.blackwell-synergy.com/doi/abs/10.1111/1467-9248.00441?cookieSet=1&journalCode=post