Dutch voters go the polls on Wednesday in an election that could see significant gains for Geert Wilders’ populist Freedom Party. He will owe his success to disillusioned Catholics

For centuries, the River Waal has been an important religious frontier. The north bank marks the start of the Protestant Netherlands, with its economic and political centres of Amsterdam and The Hague. South of the river is the historical home of Dutch Catholics – a region that once belonged to Spain, but was seized by the newly-independent Dutch Republic in the sixteenth century. It is a border that has long shaped culture and attitudes in The Netherlands. Now it is once again shaping politics, helping Geert Wilders and his Freedom Party (PVV) to become the latest populists to threaten the mainstream parties at the polls.

Electoral geographer Josse de Voogd has pinpointed Wilders’ strongholds and found that the old north-south divide is key to understanding his rise: “If you look at a map of PVV voters, then compare it with a map of this old border criss-crossing The Netherlands, you see that in almost every part of the south, the PVV does better than the national average.”

The only parts of the north where support for Wilders is anywhere near as high are the run-down edges of cities like Rotterdam and Amsterdam, where his mix of nationalism and left-wing economics seems to chime with a white working class that feels threatened by automation, immigration and an increasingly precarious labour market. But it is from the Catholic south that Wilders overwhelmingly draws his support.