Apparently they deny being anti-immigrant:
In the run-up to the polls, the SVP put up election posters of a black face accompanied by the slogan: 'The Swiss are becoming Negroes.' They also ran posters showing mugshots of criminals next to the words 'Our Dear Foreigners'. . .
Here's more press reaction, as reported in the Guardian. The Neue Zürcher Zeitung claims that high voter turnout (45.6%) helped the SVP. (How is that "high voter turnout?" And shouldn't higher voter turnout help parties of the left more?)