He announced in May, floundered in the 10% range for months until Cain dropped out, rose, stuck his feet in his mouth and sank back to the mid-teen percentage range.
His rise was a fluke. I doubt it happens again.
However, if either Santorum or Gingrich drops out, the other might garner enough to give Romney a real challenge. Otherwise, the hucka-hanger-on will cause Romney to get the nomination. IIRC, soon after SuperTuesday, most of the primaries become winner-take-all, so being even a strong #2 is moot.
I find that Santorum’s main problem is that he has trouble prioritizing his message, which is why he’s having trouble gaining traction. I don’t think Gingrich dropping out would fix this.