I also was a fan of RP until I watched an interview in which he denied evolution. (And I might point out that he is a medical doctor.)
Paul does not deny evolution. He thinks it's a pretty logical theory:
http://www.youtube.com/watch?v=iKAaps6mFYk 3:55
http://www.youtube.com/watch?v=BiVy2NbWcgo 3:50
In his book, 'Liberty Defined', he stresses that believing in evolution doesn't mean one has to reject God:
No one person has perfect knowledge as to man's emergence on this earth. Yet almost everyone has a strong religious, scientific, or emotional opinion he or she considers gospel. The creationists frown on the evolutionists, and the evolutionists dismiss the creationists a kooky and unscientific. Lost in this struggle are those who look objectively at the scientific evidence for evolution without feeling any need to reject the notion of an all-powerful, all-knowing Creator. My personal view is that recognizing the validity of the evolutionary process does not support atheism nor should it diminish one's view about God and the universe.
It seems he wants to make clear to his constituents that if he expresses a belief in evolution, he hasn't become an athiest.
Maybe his position on evolution IS a little irrational. Maybe he is a little blinded by his religious faith. But maybe he wouldn't have persisted so long in voting 'No' when every else voted 'Yes' if it wasn't for his religious faith.
Given the stakes, rejecting someone just because they have an imperfect view on something that they have no intention of legislating on, and which they would pay a heavy political price in return for no benefit if they did take the scientifically more correct stance on, isn't a good trade-off.