The Downing Theory, proposed by Anthony Downs, argues that parties form coalitions based on their ideological proximity to each other.

The Riker Theory, developed by William Riker, emphasizes the role of party size and strength in coalition formation.

The Lijphart Theory, proposed by Arend Lijphart, emphasizes the influence of institutional factors on coalition formation.

The Coleman Theory, developed by James Coleman, focuses on the role of individual-level factors in coalition formation.

The Cabinet Theory, proposed by Giovanni Sartori, argues that parties form coalitions to maximize their share of cabinet portfolios.

The Policy Agreement Theory argues that parties form coalitions based on their agreement on policy issues.

The External Factors Theory emphasizes the influence of external factors on coalition formation.

The Minimal Winning Coalition Theory, proposed by Giovanni Sartori, argues that parties form coalitions to minimize the number of parties in government.

The Party Discipline Theory argues that parties form coalitions based on their level of party discipline and cohesion.

The Cultural-Historical Theory emphasizes the influence of political culture and historical factors on coalition formation.

The Electoral Support Theory argues that parties form coalitions to maximize their electoral support.

The Issue Salience Theory argues that parties form coalitions based on the salience of issues and public opinion.

The Leadership Theory emphasizes the role of leadership and personal relationships between party leaders in coalition formation.

The Risk Management Theory argues that parties form coalitions to reduce uncertainty and manage risk.

The Institutional Design Theory emphasizes the influence of institutional design and electoral rules on coalition formation.