Open rates are going to fluctuate all the time. Personally, we do not even use "open" as a success metric since it is not an accurate measure of actually "opening" the email. Unless your content is specifically political-themed, I do not believe the Inauguration would have anything to do with it. Perhaps around the time of the Inauguration you were experimenting with new email content or email send times that were more successful than the emails you are sending now, I believe that would explain it more.
Hi Tori - I have noticed this and can't figure out why. Deliverability is still very high but I have too noticed a decline on certain emails such as our newsletters which previously had a much higher OR.