Mikey's analysis on this one seems to me to be entirely incorrect. In the first place, Ben Carson's "withering away" has so far seem him emerge as clear second in the race, in just a handful of weeks. He is now only behind Donald Trump, whose support seems to have plateaued. And this rise in Carson's ratings comes in spite of -- one might even say because of -- various "gaffes", eg his unfortunate response to the most recent mass school shooting. I don't think this latest one will affect him much either -- indeed, it might even help his cause among the more extremist wings as he can portray himself as a victim of media attempts at character assassination.
More importantly, though, I think it should be clear that Clinton would far rather face up to Carson or even Trump in the race for the White House than a candidate who actually comes across as serious. Her own campaign has had some rocky moments, particularly as she herself has been caught out for lying about using or not using a private email account for government business. The last thing she needs, then, is for the mess at the Republican party to sort itself out and leave her with some serious opposition. Ben Carson is not that opposition; Marco Rubio, probably, is.
So in short, this is not a "withering" of Carson, and it's not even the potential removal of an obstacle. More likely to make Hilary have to face an even bigger one.