I disagree with those questioning Ron Paul's motives. Nothing in his career suggests he is doing anything other than attempting to put the constitution as he interprets it front and center, and using Presidential campaigns as his evangelism tent.
Regardless of what we think of his style, the particulars of his politics, or the idiocy of his disciples, few have done more in the last several years to focus the national conversation on what are and are not constitutional functions of this government.