BRUSSELS, Belgium — Germany's Green Party long ago shed its image as an unruly bunch of shaggy haired peaceniks. But until last month's election, the idea that it could team up with Angela Merkel's conservatives in a coalition government would have seemed unlikely, even absurd.
"The chances of a coalition with the Greens have risen in recent days from theoretical to conceivable," Peter Altmaier, Germany's environment minister and a senior member of Merkel's Christian Democratic Union, told Der Speigel magazine over the weekend.
The CDU opens coalition talks with the Greens this week in parallel with negotiations already underway with its main rival, the Social Democratic Party, or SPD.
The talks are necessary because despite an unprecedented victory in the Sept. 22 election, Merkel fell five seats short of winning enough seats in the Bundestag — the lower house of parliament — to govern alone.
Whether she decides that the conservatives — whose party color is black — eventually enter government with the Greens or the reds of the SPD will decide the political complexion of Europe's economic powerhouse for the next four years.
A so-called Grand Coalition between center-right and center-left may still be the most likely option. Merkel is said to favor it, not least because the new government will need support from the Social Democrats in the upper house of parliament, the Bundesrat.
However, the SPD is reeling from a weak election performance where it garnered just 25 percent of the vote, compared to the Christian Democrats' 41 percent.
Many in the SPD believe their electoral base has been eroded by an unpopular alliance with Merkel during her first term as chancellor in 2005-2009. They want the party to rebuild in opposition in order to reclaim votes lost to the far left.
Party leader Sigmar Gabriel has indicated his willingness to enter a coalition with Merkel, but is seeking concessions on long-standing SPD aims such as a national minimum wage, relaxed naturalization requirements for immigrants, and greater investment in education and public works projects to spur economic growth.
There were signs the SPD and CDU were narrowing differences over the weekend.
In her weekly podcast to the nation on Saturday, Merkel made education a priority, hinting at more spending on schools. In an interview, Gabriel suggested the Social Democrats would be flexible in their demands for higher taxes on the rich to fund investment — a big no-no for the conservatives.
"For us, tax hikes are not an end in themselves," Gabriel told the Bild newspaper.
Another point of friction will be the share-out of key ministerial posts. Some on the center-left are demanding one of theirs becomes finance minister, which Merkel is unlikely to back.
Pressure for the Social Democrats to play hardball or even refuse to enter a coalition is coming from a woman they call "the red Merkel."
Hannelore Kraft heads the local government in North-Rhine Westphalia — the country's most populous state — and is reported to hold ambitions to run for chancellor in 2017 herself.
Kraft is emerging as a figurehead for those who view the opposition benches as the best place to prepare a comeback, rather than four years as junior partner in a government dominated by Merkel.
That prospect has increased speculation about a black-green government.
"We are approaching these talks with the Greens with the same seriousness as we do with the Social Democrats,” Hermann Groehe, a member of the CDU negotiating team, said over the weekend.
However, many on the center-right — particularly its Bavarian arm, the Christian Social Union — deeply distrust the Greens, who emerged in the 1970s as an anti-establishment, pacifist and anti-nuclear campaign group.
"I won't hold such talks. End of story," Bavarian conservative leader Horst Seehofer said immediately after the election in response to talk a black-green partnership. "Flirting with the Greens," he warned, risks prompting right-wing voters to abandon the mainstream for more radical forces.
The Greens and the conservatives have, however, worked together on the state level in Hamburg. More progressive CDU supporters in northern and western Germany may find themselves closer to the Greens than they are to the CSU on social issues, and share many of the Greens’ concerns over the environment.
The Greens, together with the Social Democrats, have voted with Merkel to back key measures to keep the euro zone together during its crisis — even as some on the right of her own party have rebelled.
Most of all, Merkel's 2011 decision to phase out Germany's nuclear power plants after the Fukushima incident and invest heavily in renewable energy has endured her to Green supporters.
Green Party members are due to vote for new leadership this week after coming in a disappointing fourth in the September election with just 8.4 percent.
Younger figures coming into the leadership are expected to be more open to entering government, and more palatable to the Christian Democrats.
"I stand for realistic political positions. It's important to me that we create a bridge to business, to the middle class," Kerstin Andreae, a leading candidate for the Green leadership said in a recent interview with SWR radio.
The Greens have been in the federal government only once before, in a coalition with the SPD from 1998-2005, when their then leader Joschka Fischer served as foreign minister.
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Germany's talks are being watched keenly across Europe.
Both the Greens and the SPD can be expected to have a moderating influence on the austerity policies promoted by Merkel's liberal allies in the outgoing administration. But with Merkel still in charge, few are expecting any major policy shift.
There’s more concern that failure to find an early solution will hamper Germany's scope for decisive thinking on some crucial euro zone issues, such the possibility Greece or Portugal could need more European cash or plans for sweeping new bank supervision and resolution rules to ensure Europe's banks don't plunge the continent back into crisis.
Warnings from leading politicians that talks could drag on into the new year are raising the specter that Germany could abandon its tradition of speedy coalition building and follow the example of neighboring Belgium, which took a record 589 days to cobble together a government after elections in 2010.