If Rudy wins some big states on super tuesday, he's back in the mix, but I think the late arrivers made a mistake, and will pay for it. People may not pay complete attention, but they know who's in the game and who's not. Rudy and Fred will likely be gone by the time the Super Tuesday votes are counted.
Even if Fred wins SC, it's still sort of like, so what? It's looking more and more like it's gonna come down to McCain, Huck, and Romney. Folks can piss and moan about the MSM all they want, but the lay of the land is well known. It's their job to overcome it.
As for why, the big three are all candidates fully in the game, fighting and winning elections for a living, and proven vote getters. Not as ideological varieties, but as individual pols. The also-rans are not - they are former minor office holders and one termers, who have backed away from serious fights in the past, and prefer consistency (by their own lights) to winning over the group in front of them.
Pundits hate the way pols win over whoever is in front of them by breezily promising and adapting and playing for the cameras and being drama queens. They think agreement with them, or perfect positioning, or at least the sort of rocklike consistency said pundits prized in (as worse, as)college essayists, "should" matter, more or instead. But they don't. Pols are the way they are for a reason. It works. It is what gobs of real people actually vote for.