Playing around with Spiegel's nifty Wahlkreis map I clicked on the 2002 results, shaded according to which party won a plurality of zweitstimme (party preference votes). Wow! I thought the US had solid colours. Talk about a north south divide (or should I say prot-catholic) divide. Southern and Catholic Germany is basically solid CDU with the exception of the industrial areas of NRW and Saarland. The reverse is also true, with the exception of Saxony, the East is solid or almost solid red. So, more interestingly, is S-H and NS which bring to mind the Prot-Catholic divide. And while I may be misremembering this, my impression was the Saxony has more Catholics than typical of the East courtesy of expellees from neighbouring (mixed)Silesia and the (Catholic) Sudetenland.

Wahlkreis map