Sweden is no longer a negative, exceptional case regarding the presence of radical right-wing populist parties. The Sweden Democrats has continually grown stronger, and in 2010 they won seats in the Swedish parliament. However, their electoral support varies considerably across Sweden. This study analyses their electoral support in 290 Swedish municipalities in order to explain this variance. Support is found for the social marginality hypothesis: electoral support for the Sweden Democrats tends to be negatively correlated with the average level of education and with the Gross Regional Product per capita, and positively correlated with the unemployment rate. The ethnic competition hypothesis, that there is a positive correlation between the proportion of immigrants and electoral support of the Sweden Democrats, is also supported.