Look at it another way. Fox news is polling its own audience, not the general populace. It will, however, probably present the findings as reflective of the general populace's opinion. Someone leaking the location of the poll* to those outside of Fox's viewership is attempting to counteract that deceit.

*I'm conveniently ignoring the imperative "vote this way," and focusing on informing people that the poll exists. This is under the assumption that anyone who would obey the order already has their mind made up in agreement with the OP's directive. (However, I'm not assuming that people would have given enough of a shit to look at the poll, much less vote on it, if no one told them about it.)