 In September 2012 she announced her candidacy for the post as head of the Socialist People's Party running against Astrid Krag after the previous leader Villy Søvndal stepped down.Vilhelmsen is said to represent the party's left wing.While most of the party leadership voiced their support for Krag and warned that Vilhelmsen's leftist line might endanger the stability of the government coalition, Vilhelmsen achieved considerable support in the general constituency of the party, and won the election with 66% of the vote.