The two main main political parties in the United States are the Democratic Party and the Republican Party.
The Democratic Party believes that there is an important role for government in improving the quality of life for people in the United States. Barack Obama is a Democrat.
The Republican Party believes that government is necessary; however, private businesses are better suited to provide services to people because a competitive business environment reduces wasteful spending. Mitt Romney is a Republican.
There are other political parties in the United States, but none of them are as well-organized or financed as the Democratic Party and the Republican Party.