Political polarization in the United States

Political polarization in the United States is the widening ideological and social divide between major political groups, especially Democrats and Republicans.

Party sorting: The alignment of political beliefs and social identities with party affiliation. As liberals and conservatives increasingly align with different parties, cross-party coalitions become less common.
Southern realignment: The gradual shift of the American South from Democratic dominance toward Republican support. It helped transform the parties’ regional bases and ideological composition.
Legislative gridlock: A failure of a legislature to enact policy because political actors cannot reach agreement. Greater partisan distance can make compromise and lawmaking more difficult.
Ideological polarization: An increase in the ideological distance between political positions or groups. This narrower form concerns policy beliefs, not necessarily interpersonal dislike.
Affective polarization: Dislike and distrust of opposing political groups, beyond disagreement over policy. It captures the growing social hostility that can accompany ideological division.
Civil Rights Movement: A mass movement that challenged racial segregation and discrimination in the United States. Conflict over civil rights reshaped party coalitions and contributed to regional political change.
Government shutdown in the United States: A suspension of some federal government operations when Congress and the president fail to enact funding. Funding disputes show how partisan conflict can disrupt ordinary government operations.
Political sorting: The alignment of political beliefs and social characteristics with party affiliation. Sorting makes parties more distinct without necessarily showing that every individual's views have become more extreme.
Negative partisanship: Political loyalty motivated chiefly by opposition to another party. Voters may unite around preventing the opposing party's victory even when their own party inspires little enthusiasm.
Reagan era: The period of political ascendancy associated with U.S. President Ronald Reagan, beginning in 1981. Conservative mobilization during this period strengthened a sharper partisan contrast.

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