By Paul Carrel, Holger Hansen and Christian Kraemer
BERLIN (Reuters) - Could an author of children's books or a former trampolinist succeed Angela Merkel as chancellor of Germany? Either is possible, and both are from the ecologist Greens.
A Greens chancellor is still only an outside chance after a Sept. 26 federal election, but the party has grown into a formidable force that is just a few points behind Angela Merkel's conservatives, who have ruled for 16 years.
With the conservatives at odds over who they want to replace Merkel, who is stepping down after the election, the Greens see a chance to win the chancellery for the first time and to stamp their progressive, ecologist brand on Europe's largest economy.
"They are within reach of the chancellorship," said political scientist Thorsten Faas.
In a sign of how seriously they are taking their push for power, the Greens have agreed to name a single chancellor candidate for the first time since they formed some 40 years ago. Previously, the party picked a leadership duo for elections, showing their commitment to gender equality but also making a tacit admission that they had no chance of winning.
Now co-leaders Annalena Baerbock, 40, a former national bronze medal winner on the trampoline, and Robert Habeck, 51, author of children's books "Flight of the Falcons" and "Cry of the Wolves", will decide amongst themselves which of them will be the party's candidate and announce the news on April 19.
Born in 1980 out of the ecologist movement of the late 1960s and 1970s, the Greens are now very much part of Germany's establishment, and they already govern the southwestern state of Baden-Wuerttemberg, a former conservative stronghold.
In a Manifesto of Principles, adopted in November, they vow to exit nuclear power and pursue an active industrial policy that helps new technologies achieve breakthroughs, especially in sectors where it can be harder to secure private funding.
They want cooperation with Russia and China but add: "Democracy and human rights are the measure for deepening relations." The party also wants to abolish the Nord Stream 2 pipeline to ship Russian gas to Europe.
Both Baerbock and Habeck are realists with an eye on power. Seen in Europe as having real prospects of governing, French President Emmanuel Macron held a private meeting with them on the sidelines of the Munich security conference last year.
Habeck, a former deputy premier and minister in the northern state of Schleswig-Holstein, is the more experienced of the co-leaders.
With a background in philosophy, the charismatic Habeck develops ideas during conversations and leaves others to work out the details, two Green party sources said. Baerbock is more detailed in her work and seeks expert advice, they added.
In a party traditionally big on promoting women's rights, some believe Baerbock should be the chancellor candidate.
"We have to allow Habeck to put Baerbock forward ... if she wants to (run)," another Greens lawmaker said.
A Forsa poll last week put support for the Greens on 23%, behind 27% for the conservative alliance of Merkel's Christian Democrats and their Bavarian CSU sister party.
Many voters are tired of the incumbent 'grand coalition' of conservatives and the left-leaning Social Democrats (SPD), who have ruled together in an awkward alliance since 2013, and for three of the four last parliaments.
"It is time for some kind of change in Germany. I would welcome change," said Kris Muenz, 21, a charity worker in Berlin. "I would probably not vote for the Greens but I would rather see them than the CDU again. This government really screwed a lot of things up."
To lead a coalition government, the Greens could team up with the SPD, which Forsa put on 15%, and the liberal Free Democrats (FDP), on 10%. Another three-way tie-up would be with the SPD and the far-left Linke.
At this stage, the more likely scenario is that the Greens join government as junior partner to Merkel's conservatives.
Naz Masraff at Eurasia, a political consultancy, put the chances of a conservatives-Greens coalition at 60%.
The party has not bickered openly over who should be its leadership candidate, in contrast to the very public divide between the CDU and CSU.
"The message to voters is clear: A party that manages its internal affairs so calmly can also be trusted with running the country," Carsten Nickel at political risk consultancy Teneo said of the Greens.
(Additional reporting by Christian Kraemer; Editing by Alexandra Hudson)