Breakthrough (Dutch political history)
After the Second World War, there was widespread feeling amongst progressives that the pillarized political system should be broken open. No longer should Roman Catholic people vote for the Catholic RKSP simply because they were Catholic or Reformed people for the Anti Revolutionary Party simply because they were Reformed. Instead, political issues should structure the political system. The progressives were united in their vision of a democratic socialist Netherlands.
In order to force this breakthrough, the socialist SDAP, the left-liberal VDB and the Christian-socialist CDU united to form the PvdA, a progressive party, which was open to all people. The new party did not, however, gain enough support under Catholics or Reformed and the PvdA became encapsulated in the socialist pillar.
In 1966, social liberal D66 attempted another breakthrough of the pillarized political system, again unsuccessfully.