That is true - McCaskill's money did help him win a slim plurality in a three-way race, which means that three fifths of Missouri Republicans voted for another GOP candidate. Why not give them a chance to vote for someone else again, someone who can actually beat McCaskill?
Because the laws of the state of Missouri don't permit it and he won the primary and what makes you think anyone else could beat McCaskill at this point and you are beginning to sound like a Democrat who wants to contest every decision and count every chad and redo every election again and again ad nauseum until they get their way ... and then want something else.
Akin is the nominee from Missouri. Get used to it.