Once you get past the fundamental qualifications of basic honesty and credibility, there are three ingredients, it seems to me, that make for a successful conservative leader.
The first (this should be obvious) is a solid conservative political philosophy. The second is charisma (like it or not, Americans prefer charismatic candidates, and it has become mandatory for the modern era).
Last (and perhaps most elusive) is the ability to effectively articulate a conservative message. This is not to say candidates must be pointy-headed intellectuals, but a leader must be able to persuasively present a serious argument for their ideas.