Far-right Sweden Democrats have grown to be Sweden’s fourth-largest party with 6.6 percent of voters backing them, the according to the latest poll from research institute Sifo.

The TT news bureau said that immigration issues were the most important selling point for the party’s supporters when they were voted into the Riksdag in 2010.

“We also see that the party has tried to widen its politics, but not very successfully,” Toivo Sjörén, head of Sifo’s polling division, said to the Svenska Dagbladet daily.

The Social Democrats receive support from 36.7 percent of voters, followed by the Moderates with 27.7 percent.