CAT5

Makes you wonder how they figured that out... Terrifying.

Voting records are public info in your states @CAT5 & @YuyoDrift, going off this list:

http://www.ncsl.org/research/elections-and-campaigns/access-to-and-use-of-voter-registration-lists.aspx. Though I feel like that's more relevant to the flurry of snail mail you'll get during election season (since for many states it's per-request.) I actually got a letter in the mail in 2018 stating my "lackluster" voting frequency (even though I've only missed one primary) and that of my neighbors of similar political affiliation.

What I'm guessing happened is that Facebook has access to your phone's geolocation data and the locations of voting centers. Like how Google asks me for restaurant reviews after I leave, Facebook probably does the same w/ your "voting/registration status". 

Yeah, that was just facebook trying to get me to register to vote. But I don't vote. This wicked-ass country can kiss my black cheeeeeeekz.