You likely have in mind something we might call "covert coercion." I might hypnotize you to vote for McCain-Palin but do it in such a way that you feel like you really want to vote for them (and if I ask you why, you'll come up with lots of reasons--they're "mavericky!" Assume you would otherwise have voted for Obama). Or maybe Professor Black gives you a sleeping pill and while you're down he does futuristic brain surgery on you to make you feel like you really want to divorce your spouse (whom Black wants to seduce) and you do it. It's very scary to think that you could be manipulated not only to leave your lover but to feel like doing so (to fall out of love), and some might argue that this is simply impossible. But we know that people change their minds (and change how they feel), so these processes just seem to be doing it faster and in a different way.
The difficulty then is figuring out how these types of manipulation, which seem like they make you unfree (and not responsible for what you do), are different from, on the one hand, slower processes that you may be aware of, such as someone offering your arguments that convince you to vote for McCain, and on the other hand, the general processes that lead you to believe what you do and feel what you feel, processes that ultimately are beyond your control. Indeed, some philosophers argue that covert coercion or manipulation is no different in principle from determinism (or, what is different, complete causation of everything that happens, including our thoughts and feelings). Hence, they think that if everything that happens is determined (or completely caused by events in the past and the laws of nature), we do not have free will.
I think these arguments are mistaken, but it is very hard to see exactly why. That is, I think that agents manipulated in these ways lack free will (to answer your question) and I think that determinism or complete causation need not rule out free will. What these cases clearly suggest to me is that free will requires that we somehow "participate in" the process of coming to think, feel, and choose as we do, that we are conscious of some of the forces influencing us (such as people offering us arguments and our considering their merits) and our being aware of what's going on has a causal influence on how we turn out (but this does not require that determinism is false or that we are somehow--impossibly--outside of the causal stream).
I hope this helps!