Partisanship

Strong, sometimes blind, allegiance to a particular political party or cause, often leading to a willingness to support the party’s positions regardless of the specific merits of an issue.

Example: The increasing frequency of straight-ticket voting, where voters select every candidate from a single political party down the entire ballot, is a clear indicator of high partisanship in the electorate.

Common misconception: Partisanship is the same as having a political ideology. Ideology is a coherent set of beliefs about politics and public policy (e.g., liberalism or conservatism), while partisanship is a psychological attachment to a specific political party, which can sometimes override ideological consistency.

Sources: https://www.britannica.com/ — encyclopedia fallback: "partisanship" as a political-science concept has no official government definition; https://www.congress.gov/ — party-line voting patterns are visible in every roll-call record on congress.gov