The poll for news magazine Stern showed The Left garnering a record 14 percent, up four percentage points, after doing well in state elections in Thuringia and Saarland two weeks ago.
Angela Merkel's conservative Christian Democrats (CDU) fell one percentage point to 35 percent, matching their share of the vote in the 2005 election. The CDU's preferred coalition partner, the pro-business Free Democrats (FDP), remained unchanged at 14 percent. At a combined 49 percent of the voter support, a potential CDU-FDP alliance is at its weakest point in the polls since the second week of January.
The centre-left Social Democrats (SPD) slid a point to 21 percent, while the Green party lost two to fall to 10 percent. As a result, an unlikely coalition between the SPD, the Greens and The Left would have only 45 percent of voter support.
But according to pollster Forsa, The Left, rooted in the formerly communist eastern part of Germany, could take more than five percent of the vote across western Germany by the time of the election itself on September 27.
Despite the gains for The Left, support remains for Angela Merkel to stay at the helm of the country. If they were to vote for chancellor directly, 53 percent of those asked would choose Merkel, though this does represent a four percentage point loss on previous weeks. In contrast, the SPD candidate for chancellor Frank-Walter Steinmeier has risen two percentage points in the polls to 20 percent of the vote.
The survey of party and chancellor preferences took responses from 2,504 Germans between September 1 and 7.