The center-left Social Democrats insist they're not interested in a continuation of the current grand coalition in which they're junior partners to the conservatives, but they're refusing for the time being to put forward their own candidate for chancellor. That decision won't be made until January.

Still, the SPD is already beginning to strike a critical note toward Angela Merkel's announcement on Sunday that she would seek a fourth term in office. The campaign is clearly on.

"It was a pretty tepid appearance yesterday, and you have to say that she seems quite winded after 12 years," SPD secretary general Katarina Barley said at a party press conference on Monday. "Mrs. Merkel has no answers to the real problems facing our country, and the concrete things that this government has done for the people of Germany were often only possible because the SPD overcame bitter resistance from the conservatives."   

The SPD contends that Angela Merkel's "myth of invincibility" is gone, but that claim will be hard to take at face value until someone gets the job of actually trying to beat her. SPD chairman Sigmar Gabriel is the most likely candidate but he has relatively low personal popularity ratings. And European Parliamentary leader Martin Schulz - the only other politician often touted as a potential candidate - is hardly a household name in Germany.

"I'm pretty sure that it will be Gabriel, and that he'll be officially named soon," Matthias Micus, a political scientist at the University of Göttingen and an expert on the SPD, told DW. "With Merkel now certain as the conservative candidate, the pressure on the SPD has now been increased."

Whoever does get the nod will face an uphill battle. He or she must position the SPD to run credibly against a party with which it has been in a coalition since 2013. And that person must also try to forge a coalition in 2017 that doesn't include Merkel's conservative CDU.

Renewed emphasis on social equity

At Monday's press conference, the SPD rejected a plan put forward by CDU Finance Minister Wolfgang Schäuble to partially privatize the Autobahn. But there are a limited number of issues on which the Social Democrats can stake out positions that clearly differ from their coalition partners.

The SPD presented a 71-page "impulse paper" at their press conference, which included abstract initiatives to reduce taxes for poorer Germans, increase government support for families and eradicate inequalities in the healthcare system.

"Our approach is to say we want to work on everyday people's problems in a rapidly changing world," said SPD parliamentary leader Thomas Oppermann on Monday. "We'll be making proposals under the heading 'more equity.'"

But it's an open question whether or not that will appeal to an electorate in times when right-wing populism and rejection of so-called "elites" is on the rise.

"I don't think it's fundamentally a problem to contest an election against a coalition partner, but you need issues," Micus said. "And the SPD lacks clear issues with which they can wage a campaign."

Micus says that he expects the SPD to move further to the left, and that this would represent their best chance for electoral success.

Differences on the left

The SPD's only realistic path for regaining the chancellorship is a coalition with the Greens and the Left Party - both of which also had critical words for Merkel.

"We'll be fighting in 2017 to end Merkel's fatal austerity policies in Europe, her calamitous lack of courage on climate change and growing social inequality," Green Party co-chair Simone Peter told the DPA news agency.

"Merkel bears a significant part of the responsibility for the deep crisis of democracy in our country," said Left Party chairman Bernd Reixinger in a statement to DPA.

But their mutual stated desire to be rid of Merkel is no guarantee that these three parties could cooperate on the national level. The Greens' environmentalism is not a priority with either the SPD or the Left, and the Left Party's cozy attitude toward Russia and criticism of the West are deal-breakers for the Social Democrats and the Greens.

Micus, however, thinks that the Left Party could be brought into line, citing the fact that the Social Democrats overcame similar disagreements with the Greens in the past.

"If the Left Party were included in a national government and allowed to name ministers, it would be extremely clear that they couldn't abrogate international treaties," Micus said. "It would be clear that international alliances can't be simply dissolved, that there are constraints and that a coalition depends on compromise."

But even if the three parties did agree, there is no guarantee that a tripartite alliance would achieve a parliamentary majority - together they are currently polling 43 to 44 percent in opinion surveys. And the SPD would also need to formulate a persuasive position on the issue on which Merkel is most vulnerable: her welcoming policy toward refugees that has led to mass migration of people from crisis regions to Germany.

The problem with the populists

That issue has been seized upon by the right-wing populist and anti-immigration Alternative for Germany (AfD), whose leader said that she was happy at the prospect of facing Merkel.

"A politician who caused the dangerous chaos in migration, which has cost billions, is putting herself up for re-election," AfD chairwoman Frauke Petry told DPA.

The AfD currently gets between 10 and 15 percent in opinion surveys, although the results of the Brexit vote in the United Kingdom and the US presidential election suggest that polls underestimate actual support for right-wing populists.

"The AfD presents the danger that a SPD-Green-Left coalition would still miss out on a parliamentary majority," Micus said, adding that another grand coalition would then be the only likely alternative. "A clear policy [on migration] is lacking right now. It all feels a bit nebulous and middling."

Opinion polls bear out that analysis. To mount a truly credible bid for the chancellorship, the SPD most likely would need to take votes away from the AFD, and it's hard to imagine the Social Democrats being able to do that right now. And that's just one reason why pollsters see a continuation of the grand coalition the SPD says it doesn't want as the most probable outcome of next year's elections.