Rand Paul. In order to affect change you first have to get elected which means you can't be viewed as some kind of radical by the sheeple and you can not be an outcast in your own party. Rand has positioned himself so he can be a real contender in 2016.
Ron Paul will be 80 years old. The man deserves some years of retirement. He can still give speeches and promote the ideas he believes in whenever he wants to.