A two-party system is a political system where two major political parties control all levels of government. The United States is an example of a two-party system in which two major parties, the Democrats and Republicans, dominate politics from local to national levels in judicial, legislative, and executive branches. Two-party systems do not mean that there are only two parties. Rather, it means there are only two parties that wield political power. This is demonstrated by the presence of the Libertarian, Green, American Independent, and other alternative parties in the United States. These alternative parties are effectively pushed to the sidelines of the United States’ political system, as major political parties have significantly more funding and media recognition than alternative parties.
This system is different from a parliamentary or multi-party system, in which different political parties must form coalitions to pass laws and form governments.
A two-party system is self-reinforcing, as opposing parties take opposite stances on issues to present a binary choice to voters. This is best demonstrated by the voting records of congress which fall closely along party lines. In 2021, over 70% of Democrats and 45% of Republicans voted for the party line more than 90%. This style of political system intentionally divides and conquers ordinary people by forcing voters to pick a side regardless of the candidate and their beliefs and abilities, rather than voting for a person they actually believe will be effective.