Suffrage - Used 30 votes in a day.
Vox populi - Used the maximum 40 votes in a day.
40 is now a new day limit for casting votes?
You now get an extra 10 votes a day but these can only be used on questions. So to get the Vox populi badge you will have to upvote at least 10 questions in addition to using the "normal" 30 votes.
See this blog post about voting for questions and the new 40 votes a day