My guess - Newt knows he's done but his ego wants the opportunity for a broadway-esque fall on your sword moment at the convention. If, against all odds, he can pull enough delegates from Romney to keep Romney from the magic number (even though that's a statistical long shot) he can go into the convention, and ask his delegates to give his votes to Santorum.
National stage, falls on sword, hero of the conservatives, blah, blah, blah. Newt doesn't have a chance to hit the delegate total, he will end behind Santorum, who will end behind Romney. Only question is whether Romney hits the magic number. And with Newt in the race, the answer will be yes.
Newt is smart, unfortunately his ego seems to get in the way of common sense a little too often...
You just may have provided the answer that has eluded us all. Ego comes first. If he drops off now like Bachmann, Cain,and Perry before him, they’d stop talking about him in the news.
With these kinds of negatives there was better reason for Perry, Bachman, or Cain to continue.