Keep in mind that there was nothing really better than Santorum or Gingrich at that time since Romney was such a dweeb. Nor was there any way that Santorum was ever going to beat Romney in the primary fight. His "Evangelical" sweater vest appeal died fast. Neither Santorum or Newt even made it on the ballot in Virginia as well, and Santorum only beat Newt because Newt couldn't beat the "conservative" media as manifested by Drudge or the Glenn Beck types.
If you have a primary with just Ben Carson and a Mitt Romney time, for example, he'd probably do okay, though he would have still lost to Romney, especially with how the primary rules are setup. But presented with the choice of a far superior candidate, the generality of the Republican electorate won't opt for the GOPe. By the way, note the retard in the link who is pulling from Carson to Rubio for some weird reason. These people in Iowa are stupid, and they are not the majority in the country.
As for the Fox polls-- they've been suspect to me from day one, since they routinely show Trump as having closer competition than any other poll put out. If Carson was ever as popular as they claimed, it never manifested itself in any verifiable way outside of Fox polls or Twitter and facebook likes.