The Green Party received 12.3 percent, an increase of 2.3 percentage points, while the Social Democrats dropped by almost the same amount, landing on 25.4 percent, according to newspaper Svenska Dagbladet (SvD).
Political scientist Tommy Möller explained that the Green Party's success largely builds on dissatisfied voters from other parties. But according to Möller, two other factors play a role in the party's success.
"One is that the deep crisis and paralysis within the Social Democrats won't last forever. The other is what effects it'll have for the Left Party that in Jonas Sjöstedt it will be getting a party leader not associated with communism. That may well be an even bigger threat for the Social Democrats," he said to SvD.
Jonas Sjöstedt is set to replace current Left Party head Lars Ohly at the party's congress in January 2012.
According to Sifo's research head Toivo Sjörén, it's going to be difficult for the Social Democrats to steal back voters from the Green Party.
However, the Social Democrat voters who've not been voting in recent elections may be lured back, since this is a core group that basically can't imagine voting for another party.
The Moderates remain the country's largest party, increasing to 34.4 percent.
Together, the four centre-right government parties received 49.6 percent, and the three left wing parties, currently in opposition, got 44 percent.
However, Toivo Sjörén pointed out that high figures for the Moderates don't mean that the governing parties have it easy until the next election, in 2014.
"Let's be clear, even after the Social Democrats' unprecedented drop in polls, those in power still don't have their own majority. If the Social Democrats climb 3 percentage units, and the Moderates drop by the same, they'll be tied again," he said to Svenska Dagbladet.
Support for the Sweden Democrats had dropped to 5.2 percent, according to the latest poll results.