With just three weeks left until the election on September 9, the party has lost most of the bounce it got in the three months after Ulf Kristersson took over the leadership last October.
The party has also fallen behind the anti-immigration Sweden Democrats in a Sifo polls for the first time since Kristersson took over, once again shedding its position as Swedens second-biggest party.
The partys Centre Party allies, meanwhile, have also been losing voters, with their support dropping from a peak of 12.9 percent in May to 9.8 percent today.
This means the the Social Democrats, Green Party and Left Party now have a combined 2.3 percentage point lead over the Alliance parties, with a combined 40.1 percent of the vote, compared to the Alliances 37.8 percent. In January, the Alliance parties had a slender one percentage point lead.
The Sweden Democrats, long-expected to be the big winners in September, have over the last three months seen their biggest fall in support since last September, dropping from 20.1 percent of the vote to 19.5 percent of the vote.
The biggest gainer has been the Left Party, which has seen its support grow steadily from 7.2 percent last August to 9.4 percent this month.
The Liberal, Christian Democrat and Green Parties have also seen upticks in support. The Green Party, which in March was polling at less than the four percent threshold required to enter parliament, is now on a much safer 5.8 percent.
The Christian Democrats, who in June were down at 2.6 percent, are now back on 3.6 percent, putting retaining parliamentary seats again within reach.
Finally, the Liberals are up one percentage point since May on 5.7 percent.