For the sake of a simple example, say you vote for exactly 601 questions and 1800 answers. Congrats, you've earned Electorate. But what if your next ten votes are all for answers? Then you'd be at 601:1810, which would put you at < 25% questions. Would the badge be taken away?
I know that the general rule is that badges never go away, but the badge FAQ does state that one of the two exceptions to the rule is when "the criteria for the badge no longer exist."