The coalition of the Green Party, Social Democrat Party and Left Party claimed 49.6 percent in the poll from Synovate, published in Dagens Nyheter (DN) and Svenska Dagbladet (SvD) on Friday.
According to DN, the headline figures are statistically significant.
The newspaper writes that the left-green parties’ lead is a result of the greater mobilization of its supporters than among the centre-right parties. The Centre Party has the largest problem in this respect with more than a fifth of its voters in the 2006 election now declining to back any party.
The far-right Sweden Democrats have meanwhile posted their highest figure yet in a Synovate poll, with 5.6 percent.
“The party has now been over the threshhold for parliamentary seats in four consecutive polls and appears to have established itself on a new level,” Synovate’s opinion analyst Nicklas Källebring told DN.
But the Sweden Democrats figures are not classified as statistically significant in polling terms, and all changes have been small for the individual parties since the January survey.
The 20 mandates that the party would gain if it maintained its voter support into the autumn election would not however be sufficient to hold the balance of power, with the opposition in a position to claim a majority of parliamentary seats.
According to Källebring, revelations over voter registration irregularities within the Moderate party in Stockholm have not affected voter sympathies.
The Moderates claimed 27.7 percent in the poll, the Liberal Party (Folkpartiet) 6.3 percent, Centre Party 4.9 percent and the Christian Democrats 4.1 percent. Only Moderates scored higher than their showing in the 2006 general election.
Among the opposition parties, the Social Democrats polled 35.2 percent, Green Party 9.7 percent and the Left Party 4.8 percent. The Green Party is now a full 4.5 percentage points over the election result and is attracting voters from across the political spectrum.