The survey, carried out by Synovate Temo and published in Dagens Nyheter, shows the Social Democrats on 42.5 percent, up 7.5 points on the general election in September.
The figure is the highest rating for the Social Democrats since December 1995. It gives the party, which in the last parliament ruled with the support of Leftists and Greens, a 0.1 percent over the governing Moderate, Centre, Christian Democrat and Liberal parties.
Together, the left-wing parties have 54.1 percent support, against 42.4 percent for the government.
The poll of 2,688 people was taken between 12th and 28th March, the weeks before and after the Social Democrats’ special conference, at which the choice of Mona Sahlin as the party’s new leader was rubber stamped by delegates.
All the changes in support for individual parties since the February rating were within the margin of error.
The full results were as follows: Moderates 25.3 (+0.1), Liberals 6.1 (+0.5), Centre 6.7 (-0.1), Christian Democrats 4.1 (-1.1), Social Democrats 42.5 (+1.1), Left 5.9 (+0.9), Green 5.8 (-0.9), Sweden Democrats 2.3 (-0.2).