The evidence on this point seems to be mixed. Consider two recent blog posts, both from academics doing excellent work. Markus Wagner of the University of Vienna studies the recent Austrian elections, in which Eurosceptical radical right parties combined for about 30% of the vote, and comments:
The EU is an important and non-negligible reason why these parties were so successful last weekend, but Euroscpeticism is by no means the only or even the primary explanation for their popularity.Instead, he argues that these parties did well because of their anti-government, anti-establishment, and anti-immigrant views.
Contrast that claim with that of another study of support for radical right parties by Werts, Lubbers, and Scheppers:
We found evidence that Euroscepticism indeed contributes to the explanation of voting for the radical right, beyond the huge effects of perceived ethnic threat and political distrust. Euroscepticism turned out to be a key political motive, actually the third-strongest socio-political determinant, to explain radical right-wing voting in Europe.So this would seem to suggest a pair of conflicting findings. Closer examination suggests that there may be more agreement between these two articles than first appears. Wagner notes:
The EU is an important and non-negligible reason why these parties were so successful last weekend, but Euroscpeticism is by no means the only or even the primary explanation for their popularity.while Werts, Lubbers, and Scheppers note:
The effect of Euroscepticism is, however, relatively smaller than of perceived ethnic threat and political distrust. Moreover, while perceived ethnic threat does well in explaining why particular social categories, i.e. lower educated people, manual workers, unemployed people and non-churchgoers are more likely to vote for the radical right than others; Euroscepticism hardly explains these differences.Suddenly, these two articles are beginning to sound very similar!
So does Euroscepticism matter in explaining radical right party support or not?
I think the answer is yes (but, then again, I might be biased!). But that is a qualified yes for important reasons. First, national context matters. Wagner is right to highlight the effects of the grand coalition (as I also suggested here) and perceptions of corruption on radical right party support in the 2013 Austrian election. National context probably explains the failure of Eurosceptical parties to gain much traction in Germany as well. Second, party quality matters as well. The Austrian Freedom Party have been quite effective campaigners, while the National Democratic Party of Germany is probably a bit extreme to win many votes (though the danger of tautology in claims like this is pretty obvious).
Probably the most important reason for a "qualified" yes is that Euroscepticism is one of several issues emphasized by radical right parties, which can be hard to disentangle as they all revolve around a defense of the nation. In addition to Eurosceptical positions, radical right parties also tend to take anti-immigrant, anti-establishment, and occasionally anti-globalization positions as well. Elsewhere, I argue that the common thread is that these tap into a broader authoritarian worldview emphasizing national sovereignty and solidarity. The result, as I suggest, is that attitudes towards the EU, national pride immigration, and religious hostility are related. The result is that it is difficult to identify just what role Euroscepticism plays (and it is surely less than more proximate concerns like immigration), and its effect probably varies by country. Nonetheless, I suspect that Euroscepticism is an important factor driving radical right party support in many countries, as the Werts, Lubbers, and Scheppers study argues--but certainly not the only one. Given the increasing salience of European concerns, particularly during the recent eurozone economic crisis, this is a topic that merits further investigation.