The desire to win elections and form a government is what distinguishes a political party from other social institutions.
A political party is an organized group of people who share similar political opinions, principles, interests and beliefs with the aim of winning election and control of government of a country/state/municipality.
On the other hand, there are social institutions such as pressure groups, A pressure group may be defined as an organized social interest group which is formed with the main aim of pursuing its interests and government policies to the interest of its members without any intention to control the government.