Another problem is SC is an oPen primary state... So you know Dhimicrats will be out in force for Willard.
The conventional wisdom outside of FR, in "mainstream" media is that Romney is the strongest candidate vs. Obama. I don't necessarily agree with that, partly because my opinions are not those of elite liberal media.
But Democrats and many independents are the product of the left wing media. Your assumptions is that all these Democrats and independents all read FR, they found here that Romney is the weakest candidate, and therefore, in open primary are going to vote Romney, in order to weaken GOP, strnghten Dems..
That, to me, is just not intuitive. Open primary will result in more of the less conservative voters participating. But it is not a conspiracy to give GOP the weakest candidate. It is just that they (some Democrats - mostly "former" Democrats, and some independents) have found a candidate they liked.