First off- by "opt out of moderator elections" I assume you mean the voting notifications. (As you don't get forced to run in an election). As already mentioned, there are a lot of notifications we want to filter out. Fortunately, by pressing the notification box on Stack Overflow or any other stackexchange site, the notifications are cleared. The election notifications are just like any other notification: Dismissable.
No notification requires you to press it, so if you don't want to vote, press the notification box and it goes away (notification box != the notification, it is the box you hover/press to see all notifications). You can ignore any and if you want all notifications you get.
But no, there is currently no notification filters and no way to block moderator election notifications.