Contrary to _dilerium's answer, I think this, in at least Sweden, was a quite significant factor. But that must(?) have changed now. During the last wave of immigrants coming to Sweden, the whole range of parties, except for the Left Party, made a 180 degree turn and agreed with the Sweden Democrats narrative. Even the Social democrats are now saying that Sweden is under a social and economic collapse due to immigration which was lauded by the Swedish Democrats.

See for example [0] (Swedish) and links within.

http://www.dn.se/nyheter/sverige/internationella-medier-sver...