In 2009, Frank-Walter Steinmeier specifically moved to a safe SPD district in Brandenburg so that he could finally win a Bundestag seat. The second criteria for choosing the district: Geographically, it's pretty close to Berlin, so he doesn't have to travel too long. Of course, he had no prior connections to the state of Brandenburg whatsoever.
Well, "safe", he won only by 5%.
Well, if we count only fully free and fair elections, 2009 was the SPD's worst election result since, um, 1932 I think... winning by 5% is still pretty good under such circumstances.
Bottomline is, the SPD had won this district in every election since 1990 and that's why Steinmeier chose it.