In the picturesque German city of Potsdam, a crowd gathers at the main square where a band is playing innocuous 1980s covers.

The friendly-looking musicians on stage attempt to rouse some enthusiasm from those waiting to hear Martin Schulz — the main challenger to German Chancellor Angela Merkel in Sunday's elections — speak at a campaign rally.

Some among the throng are trying to escape after taking a wrong turn on their way to a Prussian palace or museum, like 64-year-old Anton Warzecher, who says he has already made up his mind and does not need to hear another pitch from Schulz.

"I'm not convinced by Martin Schulz; he's not a plausible candidate," Warzecher says. "I simply don't trust his ability to deal with all the tensions in the world right now. Only Angela Merkel can do that job."

Warzecher's view is reflected in the opinion polls, which, for weeks now, have seen Schulz's Social Democrats, or SPD, lagging up to 15 points behind Merkel's conservative bloc.

When Schulz announced his candidacy earlier this year, he appeared to have a fighting chance. Now, Schulz is lagging far behind, and the Social Democrats could be in for its worst result yet.

Christiane Hoffmann of the weekly magazine Der Spiegel recalls how much hope there was when Schulz first challenged the chancellor.

"Under the surface, there is an urge for change in Germany," Hoffmann says, "and this was shown in the beginning of the year when Martin Schulz entered the political arena."

The SPD gained thousands of new members, and it looked as if it was going to be a real race. Hoffmann says this changed: "Martin Schulz wasn't able to give voters the feeling that he really himself believes he would be a better chancellor than Merkel."

Back in Potsdam, where a modest-sized crowd of SPD supporters politely cheer their candidate to the stage, that urge for change is more or less palpable.

Julia Zimmerman, a retired teacher from Potsdam, says she is not paying too much attention to the polls. She is worried about her pension and looking to Schulz for solutions.

"I think he's a bit more of a fighter than Angela Merkel is presenting herself at the moment," Zimmerman says. "I have nothing against Angela Merkel. What I would like is a bit more movement. I'm of the opinion that things should be different."

What Schulz lacks in support, he makes up for with zeal. The former president of the European Parliament is a passionate orator. Returning to domestic politics after years in Brussels, he is well-aware of how the outside world perceives Germany. Schulz addresses this at the Potsdam rally.

"Not everybody in Germany is well-off," Schulz says. "But we're constantly told that 'Germany is a strong country, and everybody's doing fine.' That simply isn't case."

Cautiously, Schulz adds, "I'm not bad-mouthing our country; I'm simply trying to improve things."

Political commentators in Berlin argue that Schulz's handicap is that his party spent eight of the past 12 years in coalition with Merkel's Christian Democrats. They say Schulz can hardly criticize the chancellor when their policies are barely distinguishable from each other.

At a recent press conference, Schulz attempted to dodge questions about whether the SPD would join yet another grand coalition. Laughing, he insisted, "My aim is to become chancellor. If Mrs. Merkel wants to join my cabinet as vice chancellor, she's more than welcome."

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