Fair question. I agree that there is a lot of overlap between conservative and libertarian thought. The kind of conservatism advocated by Paul makes a conscious effort to divorce itself from any faith based justification for its belief in free and unfettered markets. Carried over into social issues it results in a pretty bizarre set of justifications for a laissez-faire approach to abortion, sexual behavior of all kinds, legalization of drugs, etc. It is as if the individual is set free, but without much responsibility except to oneself and to the market.
The Republican party is, IMHO divided among the eastern, establishment (once called the Rockefeller wing) which is fiscally conservative but socially moderate to liberal, followed by another group that is fiscally conservative but socially moderate (but not to the extent of the libertarians) and the values voters who are fiscally and socially conservative although a portion of that group is moderate to liberal on the fiscal side.
While it might be argued that Paul falls loosely in the second category, and I would not object to that, his tendency is simply to disrupt things in the Republican process, and then turn around and endorse the Libertarian candidate. That, as much as anything, tells,me who he is. That's fine, but I think he is dishonest in that regard and ties up a lot of votes that would go to another conservative in the race, in this case almost guaranteeing a Romney nomination.
I misspoke. He runs Republican then endorses outside the Republican party, I.e. Chuck Baldwin and Cynthia McKinney.
Why does an individual have a "responsibility" to not ingest certain substances or engage in certain consensual adult sexual behavior? Those acts violate no other individual's rights. They may affect other individuals - but that's far too broad a standard for governmental action, as almost everything anyone does "affects" someone else in some way.