The attackers screamed at terrified Emilia Orpana calling her a whore and a racist as she campaigned in Nynäshamn, 35 miles south of Stockholm.
She was working at the polling station when she was targeted by the thugs.
Ms Orpana said was terrified of being kicked in the stomach and added: “I felt very worried and afraid”.
Another representative for the party and a third person who had come to vote were also verbally abused by the two youngsters.
Ms Orpana told Swedish newspaper Aftonbladet: “He said he would step on my colleague’s head and kill us.
The two men also tried to grab the two members of the Sweden Democrats and take their ballots.
Ms Orpana said the attacker called her a “racist” and a “whore” and spat at her.
She added: “I was terrified he was going to hit me in the stomach as I’m pregnant.”
When it became clear Ms Orpana was being threatened, members of the other parties present at the polling station came running to help out.
Ms Orpana said: “I feel grateful to my colleagues from the other parties for running over to help.
“It was a fine democratic act. They showed that any act of violence is not acceptable no matter whom you’re voting for.”
Police in Sweden confirmed the attackers struck just before 10.30 today – two and a half hours after the polls opened.
No one was physically injured and the event is currently being investigated as an unlawful threat.
Leader of the Sweden Democrats, Jimmie Akesson later commented on the incident.
He said: “I think there have been an unusually high amount of attacks on people out rallying for their parties in this election.
“It is a very sad development.”
Prime Minister Stefan Löfven also commented on the attack.
He said: “That an incident like this occur in Sweden shows how important it is that we stand up for democracy and everyone’s equal worth.
“We must make sure we decrease inequality so people will stop doing similar acts in the future.”
Another threat has also been reported in connection with the election.
Politician Ann Heberlein from the Moderate party has reported a man walked over to her and called her “fascist” outside a polling station in Lund, southern part of Sweden.
She told Swedish newspaper Aftonbladet: ”None of the people who were there intervened. It was only when my husband got there the abuser left me alone,”
Ms Heberlein added: “He said I was against everything good in this world and that the entire population of Sweden hates me.”
“He called me ‘pussy’, ‘fascist’ and ‘whore’”.