Both politicians are women, both grew up in East Germany and both have lived with Lutheran pastors.
Angela Merkel’s father was one, as is the husband of Katrin Göring-Eckhardt, one of two Green Party front runners in September’s general election.
One question will eclipse all others at the Green Party conference which starts this evening: will Ms Göring-Eckhardt make the previously unthinkable leap into a coalition arrangement with Dr Merkel’s Christian Democrats (CDU)?
Officially, the Greens are fighting for a return of the SPD-Green coalition that ruled for seven years until 2005. But a stumbling start by SPD front-runner Peer Steinbrück has left the SPD-Green alternative 10 points shy of Dr Merkel’s ruling coalition and well short of a majority, according to a new poll.
If the German leader fails to win a majority with her current Free Democrat (FDP) partner, meanwhile, Dr Merkel faces a second grand coalition with the SPD or the as yet untested Green option.
Interestingly, the new Forsa poll indicates that a majority – 54 per cent – of Green supporters would back an alliance with the CDU if the numbers add up in September. Almost two-thirds of CDU voters (64 per cent) are similarly inclined.
The poll numbers reflect a shift in German politics over the past decade. Dr Merkel’s CDU is an increasingly pragmatic party of the centre while, after 30 years, voters and leaders of the Green Party are older, better off and more conservative.
“Green supporters come more from the middle classes and hardly at all from the working class,” said Forsa analyst Manfred Güllner.
Sinking ship
Ahead of the party conference, Green Party MEP Daniel Cohn-Bendit has expressed "sinking optimism" about Mr Steinbrück's chances and urged the party not to lash themselves at all costs to the mast of a sinking SPD ship.
"CDU-Green would be a realistic option under certain conditions. That's something we cannot conceal," he told Bild yesterday. "The conditions would be: finance and energy ministries for the Greens and a CDU shift on gay marriage and minimum wage."
A decade ago, that list of Green demands would have been far longer. Movement on tax privileges for gay couples is looming in the constitutional court while Dr Merkel is already edging her party towards the previously taboo idea of backing a statutory minimum wage.
Other age-old friction points between the CDU and Greens have vanished: the CDU dismantled compulsory military service and, after the Fukushima disaster in 2011, Dr Merkel performed a U-turn on nuclear energy.
Green Party analysts insist there are still big gulfs on security, immigration and fiscal affairs. They want relief for lower and middle incomes and higher taxes for top earners – a no-go for the CDU. Greens are equally unimpressed by the CDU’s continued tough line on migration and security matters.
Lively clash
With the spectre of Angela Merkel in the background, this weekend's conference will be a lively clash between the Green Party's two factions, the pragmatic "realos" and the more dogmatic "fundis".
While the party’s rank and file remains a colourful “fundi” mixture, Ms Göring-Eckhardt and her running-mate, former environment minister Jürgen Trittin, are both considered to be politically ambitious “realos”.
On their watch we will learn whether, in German politics, opposites really do attract.
