"The problem with so many radical candidates is that they lack political sense as well. Bachmann is a potent combination of substantively radical and politically shrewd, much like [Paul] Ryan. And if Ryan does not run, Bachmann could make some noise."
Subtext: Distinguish Bachmann and Palin on the sanity/intelligence axes. Palin is the stupid one, so Bachmann is the crazy one. With the negatives nailed down, we may concede that Bachmann is pretty smart (watch out!) and Palin is pretty sane (now, go home take care of your children).