The Social Democrat, Left and Green parties, which ran on a common platform in the 2010 elections, got the approval of just over half of the 1,930 people polled by Sifo, for newspaper Svenska Dagbladet.
This means a lead of 11.7 percent over the government parties. But in the same period before the last election the centre-right Alliance was also behind in the polls, by almost the same amount, 10.4 percent.
Of the people polled fewer than 4 percent said they would vote either Center or Christian Democrat. If this is reflected in the election, these two parties will fail to make it into the Riksdag, meaning an even greater victory for the opposition. In reality these two parties are likely survive due to tactical voting.
The big difference between the polls before the 2010 election and the latest poll is the support for the Sweden Democrats, an anti-immigrant party that has been hit by recent racist scandals, but still attracts greater and greater support: 9.2 percent in this poll, double its figure in 2010.
If neither the red-greens nor the Alliance gain over 50 percent the Sweden Democrats will hold the balance of power in Swedish politics.