 The SDP scored its biggest electoral triumph to date in the spring of 1910 when Emil Seidel was elected as Mayor of Milwaukee.One key factor behind socialist success in this race was a breakthrough by the SDP among working class Polish-American voters, who had traditionally supported candidates of the Democratic Party.Seidel's victory capped a decade of steady SDP growth in Milwaukee mayoral elections, in which the party's candidates had seen the number of socialist votes cast grow by a factor of 8 between the election of 1900 and the end of the decade.