In a survey for Stern magazine, pollster Forsa found only 20 percent of Germans were prepared to vote for the SPD on September 27. The last time the SPD saw such dismal levels of support was back in August 2008.
The party's rating dropped three percentage points from last week's poll, but it did not take into account the election campaign launch of the SPD's chancellor candidate Frank-Walter Steinmeier on Monday.
The SPD now trails Chancellor Angela Merkel's Christian Democratic Union (CDU) by 17 percentage points – with the conservatives down one point at 37 percent this week. Their preferred coalition partners, the pro-business Free Democrats (FDP), rose one percentage point to 14 percent, giving a potential centre-right alliance a solid 51 percent majority.
The environmentalist Greens also rose one percentage point to 13 percent and the socialist party The Left improved two points to 11 percent.
Forsa polled 2,502 people across Germany from July 27 to 31.