All of the Newt people would vote for Santorum because they are conservatives, but a lot of Santorum voters would not vote for Gingrich, because they are Romney types, which means the majority of Santorum voters would enthusiastically switch to Romney.
The biggest problem for Newt is that people perceive him as a braggart, an authoritarian, and opportunistic.
He didn’t run because he thought he would have a chance, thats why he took off during his “campaign” to go on a cruise with Calista as his staff abandoned him in disgust, he ran because it ups the price for speeches and such.
Even during the first debates this time, right here on FR, people said he was a good debater, but he was Newt the RINO.
Now all at once he is a stalwart conservative hero. LOL