Introduction The fi rst nationwide political party in the Netherlands was the orthodox Calvinist Anti-Revolutionary Party (ARP) that was founded in 1879 (see, for example, Koole 1995: 17). With the introduction of universal suffrage and a system of proportional representation (PR) in 1917, nation wide parties became the standard model. The Dutch party system has always been very open and partly as a result fragmented, especially when compared to other countries. Due mainly to the system of PR in a single, nation wide electoral district and the low electoral threshold of originally 1% and from 1956 onwards only 0.67% of the total vote, new parties have easily been elected into Parliament. From 1922 to 2013, the politically dominant Second Chamber or Lower House of the bicameral Parliament always contained representatives from 9 to 14 political parties, of which at least seven parties can be considered to have ‘coalition-potential’ (Andeweg and Irwin 2009: 55).