Because these two parties are so powerful, the United States government is often called a "two-party system." Some would refer to this as a Duopoly because they are the main political parties and they run the government.
How and why were political parties established in the United States and what is their purpose
The Electoral College is a body of electors established by the United States Constitution, which forms every four years for the sole purpose of electing the president and vice president of the United States.
What is the Electoral College and how are the electors appointed?
What are the the three branches of government and why are they necessary in a Federalist System?
To ensure a separation of powers, the U.S. Federal Government is made up of three branches: legislative, executive and judicial. To ensure the government is effective and citizens' rights are protected, each branch has its own powers and responsibilities, including working with the other branches.