A political party is a political organization that typically seeks to influence government policy, usually by nominating their own candidates and trying to seat them in political office. Parties participate in electoral campaigns and educational outreach or protest actions. Parties often espouse an expressed ideology or vision bolstered by a written platform with specific goals, forming a coalition among disparate interests.

The freedom to form, declare membership in, or campaign for candidates from a political party is considered a measurement of a state's adherence to liberal democracy as a political value. Regulation of parties may run from a crackdown on or repression of all opposition parties, a norm for authoritarian governments, to the repression of certain parties which hold or promote ideals which run counter to the general ideology of the state's incumbents (or possess membership by-laws which are legally unenforceable).

Furthermore, in the case of far-right, far-left and regionalist parties in the national parliaments of much of the European Union, mainstream political parties may form an informal cordon sanitaire which applies a policy of non-cooperation towards those "Outsider Parties" present in the legislature which are viewed as 'anti-system' or otherwise unacceptable for government. Cordon Sanitaires, however, have been increasingly abandoned over the past two decades in multi-party democracies as the pressure to construct broad coalitions in order to win elections - along with the increased willingness of outsider parties themselves to participate in government - has led to many such parties entering electoral and government coalitions.