It seems to me that if one person puts one sword in the hands of the opposition, the rest of us should first give him a couple extra and then start swinging ours even harder.
I don't put much stock in the notion of a viable third party candidate. This isn't Alaska, it's Missouri, and the political dynamic is different. All a third party run would do is solidify a McCaskill win. If it's a choice between McCaskill and Akin, I know where I'd cast my vote (if I could, but I don't live there).