My CTR has been down recently so I looked at my site from multiple geo-locations and saw a bunch of political ads.
Example: Looking at the site from Las Vegas showed a huge Harry Reid ad. 336x280 with only a single ad listed in the ad box.
I've turned off "interest-based" ads a long time ago. (cleared browser cache too before checking). I have no clue what Harry Reid has to do with Sports (one of my websites) or Health and Depression (another site).
Anyway, I turned off "Politics" in the Ad Review Center under Adsense Setup (didn't even know this setting was there). That seemed to help a bit.
I just wanted to warn people if their CTR seemed off. Check for all these political ads that have NOTHING to do with your content.