Demoralised and divided, Germany's oldest party is in serious trouble after 11 bruising years in power in two different coalitions, with even the country's federation of trade unions refusing to offer its traditional support.
When the SPD's Gerhard Schröder was first elected chancellor in 1998, the party won 40.9 percent of the national vote. This time around, opinion polls indicate it is on course to notch up to about 25 percent.
In contrast, Chancellor Angela Merkel's centre-right Christian Democrats (CDU), the SPD's current partners in an unhappy "grand coalition," are riding high in the polls between 35 and 39 percent.
And with surveys indicating that Merkel will be able to ditch the SPD and instead form a government with the pro-business Free Democrats (FDP) after the election on September 27, a period of opposition for the SPD looms.
"It's all over," Wolfgang, 50, told AFP at a party rally in the southern city of Stuttgart last week, a gathering marked by a distinct whiff of resignation.
"If we score 28 percent it will be amazing," agreed civil servant Sybille Kirschbaum, 54. The result would be worse than the SPD's post-war record low of 28.8 percent recorded back in 1953, the year before Merkel was born.
The party's problems date in part back to Schröder's time in office from 1998 to 2005, when he governed in a coalition with the environmentalist Greens that introduced a barrage of painful social security and labour market reforms.
These were seen among many of the party's rank and file as a betrayal of the SPD's socialist principles, sending many into the arms of what in a short space of time has become a new force in national politics: hard-line socialists The Left.
This new party, a collection of disaffected SPD members and former communists from the old East Germany, is now represented in 11 of Germany's 16 state parliaments and is polling at around 12 percent nationally.
It has also poached SPD voters by being the only party calling for an immediate withdrawal of Germany's 4,200 troops in Afghanistan - a deployment that begun under Schröder and which the SPD continues to support.
The SPD works with The Left to form state coalitions, but at federal level the party leadership has made it clear that this is taboo.
Governing with Merkel has also made it hard for the SPD to score points against the CDU, even with Germany crippled by its worst recession since 1945 - something that normally could be expected to boost the left.
This problem is nowhere more evident than when it comes to the SPD's candidate to replace Merkel, Frank-Walter Steinmeier, deputy chancellor and foreign minister in the "grand coalition."
"Government successes are attributed to Merkel, not to Steinmeier," political scientist Nils Diederich told AFP.