Spiegel Online has a really fun interactive map of election results. It shows a map of Germany broken down by district, and you can filter by party to see how well each party did. Of course, the most dramatic results confirm an old insight: votes for the more extreme parties are concentrated in the East. One commentator on whatever TV program Der Spiegel’s livestream was broadcasting made the point clearly: Ossis had authoritarian regimes from 1933 right up to 1989, and the tendency hasn’t been trained out yet. Other people would say that German authoritarianism was born there. Whatever the cause, it’s noticeable.
Here are the results for "strongest party." Union dominates the map, but less so in the East. You can see the border. Notice also that the only districts where the AfD came in first are in the East.
(By the way, the blue is the CSU, a party that only runs in Bavaria, and in place of the CDU. So, the fact that it exactly traces the Bavarian border has a straightforward explanation.)
Speaking of the AfD, its support is less regional than a lot of people would like to think. Nevertheless, you can see the border here quite clearly.
Where you really notice it is for the Left Party. The border is extremely salient here. Basically no one in the West votes Left (except in the Saarland, where the party was born). Yes, Die Linke/Left Party is more or less the successor party to the old East German ruling party, the SED. Something to think about before buying the assumption that East Bloc regimes were universally unpopular. They were unpopular, but it’s complicated.
If you play around a little more there are two (or one, depending on how you look at it) other interesting things: choose the option for strongest showing for FDP and the Green Party, and you’ll notice that they both seem to have strongholds in Baden-Württemburg. What’s up with that? My interpretation – it’s the yuppie vote. I guess a lot of comfortable middle class people live there.