To win you need a ground game, you need people to nudge others to caucus or to vote for you with a get the vote out effort, you need internal polling and you need to ground and pound the early primary counties in states not hold 1 or 2 rallies in stadiums. Trump has no ground game, no get out the vote effort and he doesn't even have all the precinct captains in Iowa get to caucus for him. In this part of the primary Donald can have those crowds if he can't mobilize them then he's this cycles Howard Dean then so be it.
One other data point: In 2012, Newt was getting MUCH bigger crowds than Myth, even through the Florida primary. To the point where Myth assigned hacks like Jason Chaffetz (whose face makes me want to throw something at the TV to this day) to heckle him at his campaign events.
Hank