German Vice Chancellor Sigmar Gabriel and Chancellor Angela Merkel at the weekly federal Cabinet meeting | Adam Berry/Getty Images SPD’s Sigmar Gabriel won’t take on Merkel The Social Democrat leader says Martin Schulz has a better chance of beating Angela Merkel.

Sigmar Gabriel will not challenge Angela Merkel for the German chancellorship in this year's elections and has proposed former European Parliament President Martin Schulz as the Social Democrats' candidate instead.

Gabriel described it as his "duty as party leader" to step aside in favor of Schulz, who was given a much better chance in the elections by internal party polling that the SPD leader commissioned.

"It was not an easy decision but I'm convinced it was the right decision," Gabriel told reporters late Tuesday.

“If I stood in the elections, I would fail and so would the SPD,” Stern quoted Gabriel as saying. Gabriel, who is currently vice chancellor and economy minister as well as chairman of the SPD, will hand the party leadership over to Schulz as well.

Gabriel's decision, which he revealed in interviews with Stern magazine and the weekly Die Zeit, came as a surprise even to his closest party allies. Though he had been struggling with the decision for months, most of his associates assumed he would take up the party mantle.

In recent months he appeared to be laying the rhetorical groundwork for a run. He even allowed a TV documentary maker to follow him and his family for an intensely personal film about his life and political ambitions. His wife speculated openly about what life would be like if he became chancellor.

"I didn't think he was the type to commit suicide before death," one longtime colleague said.

In explaining his decision internally, Gabriel cited polls he commissioned which indicated that he would lose a head-to-head confrontation with Merkel. Nonetheless, he was torn, party colleagues say. The same studies indicated most Germans thought he was capable of executing the office. In other words, Germans thought he could do the job. They just didn't like him.

He was also angered by what he considered the media's violation his privacy. Before Christmas, Gabriel, a corpulent figure who suffers from diabetes, underwent surgery to reduce the size of his stomach. A report of the procedure appeared in the tabloid Bild newspaper.

Gabriel's dilemma was that he had virtually no realistic possibility to close the massive gap between the SPD and Merkel's conservatives. Yet Gabriel also knew that he would not be able to hold onto the party leadership if he didn't run, his associates said. He managed to avoid running in 2013 by fielding former finance minister Peer Steinbrück as the party's candidate. The party finished a distant second.

Difficult times

After nearly eight years at the helm of Germany's oldest party, not running running this time around was not an option for Gabriel, a protege of former chancellor Gerhard Schröder.

At the same time, Gabriel, a career politician who came up through the party's youth organization, didn't want to leaving politics altogether. Married with one child and another on the way, he was keen to retain an influential and lucrative position as a minister, his colleagues say. He saw an opening to step from the party leadership after he succeeded in maneuvering current Foreign Minister Frank-Walter Steinmeier into position for the German presidency. Steinmeier is expect to be elected by Germany's parliament and regional representatives next month. That would pave the way for Gabriel to succeed him in a position that is generally considered the second-most prestigious in the German government.

"In these difficult times, the country needs new leadership," Schulz said at a press conference in Berlin. "There will be no Europe-bashing from me," he added, saying he would fight against populism and "enemies of democracy" as "Social Democrats have always done."

Brigitte Zypries, who is a minister in Gabriel's department, is to take over the economy portfolio.

Merkel's conservatives are far ahead of the SPD in voter intentions for September's elections. In the latest Deutschlandtrend poll, support for the combined Christian Democrats and Christian Social Union stood at 37 percent, with the SPD trailing far behind with 20 percent. The far-right Alternative für Deutschland were third in the poll at 15 percent.

Peter Tauber, the general secretary of Merkel's Christian Democrats, said they were relaxed about the SPD's decision as they had "better arguments, better policies and better candidates."

He said on Twitter that the party would go into the campaign with a moderate and centrist message.

SPD parliamentary leader Thomas Oppermann said Gabriel had "put the interests of the party ahead of his own."

But Andreas Scheuer, general secretary of the Christian Social Union, Merkel's Bavarian allies, said Gabriel had left behind "a heap of rubble" and Schulz was the candidate of last resort.

Alternative für Deutschland leader Frauke Petry branded Schulz a "symbol of EU bureaucracy and a deeply divided Europe."