Adam - I went through Martin Erler's 1995 catalogue "The Stamps of the NSDAP (Nazi Party) and Its Sub-Organizations", all 93 pages, and I did not see your stamp listed. The catalogue is very well-illustrated, so if it were in this work I would have seen it.
Just trying to eliminate a possibility there…
I did learn that the image was taken directly from a propaganda poster:

This was created in 1932 and was one of the first (if not the first) propaganda poster… it was also used in an election for leader of the Nazi party, apparently. So it is entirely possible that this is an ELECTION stamp.
Here is a little more on the subject, perhaps this would enlighten us a bit more - but my personal assessment is that this is a 1932 election stamp to match the posters that were being plastered all over Germany (with and without the dot over the "i"). Here's a link to more information, in case any one is interested:
https://designobserver.com/feature/...ndbook/24898Barry