I haven't found exact numbers of migrating workers from other EU-countries that live and work in the Netherlands, it could be around 1 million people. Normally the European elections are not very popular among most voters. But this could change if people start to understand the reality of the EU-project. Especially migrating EU workers are confronted with this reality. The question political parties should try to have a coherent answer to is the notion of EU-citizenship.
A study has been done by Dita Vogel, sponsored by EU called "POLITIS" on the importance of migrants for democratic development within the EU memberstates:
Dr.Vogel believes that the results of the project will help to raise awareness of the importance of bringing immigrants onboard in civic and political society. To facilitate this process further, the POLITIS project consortium has set up a training course called 'WinAct' to help officials from trade unions and political parties recruit immigrants as active members. Often these organisations do not know how to approach immigrants adequately and how to motivate them for long-term membership and collaboration.
I understand from the website that Mustapha Laboui, projectmanager for ethnic minorities of the dutch tradeunion FNV was the only representative of a dutch organisation involved in Winact. A report on his efforts related to this issue called "innovative trade union strategies" can be found on the FNV website.
The international migration institute at the University of Oxford dedicates a research project to the subject of migration and democratic development.
It's also interesting to see how visible the campaign for the ratification of the UN convention on Migrant worker and their families will become in this upcoming election.