 It has been argued that single-member districts tend to promote two-party systems (with some regional parties).Called Duverger's law, this principle has also been empirically supported by the cube rule, which shows how the winning party in a first-past-the-post system is mathematically over-represented in the final chamber of representatives.Supporters view this effect as beneficial, as parliamentary governments are typically more stable in two-party systems, and minorities do not have undue power to break a coalition.