The primary function of political parties in a democratic system is to nominate candidates for elections and compete for control of government.

Ideology, or a person's political beliefs and values, is generally regarded as the most influential factor in determining party membership.

Partisanship refers to the psychological attachment and emotional connection individuals have with a political party.

Selective perception suggests that individuals tend to seek out information that reinforces their existing beliefs and avoid information that challenges them.

Political homophily refers to the tendency of individuals to form social networks with others who share their political views.

In multi-party systems, social class is often a significant factor in determining party membership, with different parties appealing to different class interests.

Party recruitment refers to the process by which individuals are attracted to and join a political party.

In two-party systems, ideology is often the primary factor in determining party membership, with individuals aligning themselves with the party that most closely matches their political beliefs.

Party defection refers to the process by which individuals leave one political party and join another.

In single-party systems, ethnicity is often a significant factor in determining party membership, with different parties appealing to different ethnic groups.

Party switching refers to the phenomenon where individuals change their party affiliation over time.

In emerging democracies, economic development is often a significant factor in determining party membership, with different parties appealing to different economic interests.

Political participation refers to the phenomenon where individuals become actively involved in politics, including joining political parties and engaging in political activities.

In developed democracies, ideology is often the primary factor in determining party membership, with individuals aligning themselves with the party that most closely matches their political beliefs.

Party defection refers to the process by which individuals leave one political party and join another, often due to dissatisfaction or disagreement with the former party.