Since legalization of prostitution hasn't come up as an issue, I believe Ron Paul is the only candidate, who supports the legalization of prostitution. That is a legal, not a moral concept.As George Carlin always said, selliing is legal, f#$%ing is legal. Why when you combine the two is it illegal?
You can be an person of strong morality and oppose writing that morality into the law. In fact, writing morality into law is in itself profoundly immoral. That takes the option of moral action away from people and makes the consequences of immoral action worse.
For example, in the case of prostitution, you can make the case that making it illegal is worse for the women, it's worse for the community and it creates corruption within the police and legal systems.