With Euroskeptic parties being on the rise across Europe, dominant parties are pressured to reconsider their stances on European integration issues. Dominant parties' reactions to challenges by Euroskeptic parties must not be limited to the national level but are also required at the sub-national level since in many European Union (EU) member States the EU's Cohesion Policy is directly targeted at the regional level. Therefore, EU issues should also matter at the regional level. Transferring theoretical arguments for party competition at the national and European level to the sub-national level in Austria, Belgium, the Czech Republic, Germany, Spain, the Netherlands and the United Kingdom (UK), we argue that sub-national dominant parties will become more Euroskeptic when faced with electorally successful Euroskeptic challenger parties. Using a novel data set on sub-national parties, our preliminary results for Germany, the Netherlands, and the UK show that overall dominant parties do not react to electorally successful Euroskeptic challenger parties, but if they react then they rather adopt more pro-European than more Euroskeptic positions.