I don’t see Trump dropping out of the top 3 in NH. He starts with too big a lead and has a somewhat narrow but loyal following that can’t be swayed no matter what.
I think there is a chance, albeit still a small one, that Rubio winds up winning NH with Trump coming in 2nd again and Cruz or perhaps Christie coming in 3rd. NH is probably just not going to be a great state for Cruz, but he should do well in SC. The thing to watch in NH is if Rubio can beat Trump. That would be 2 second place finishes for Trump which for most candidates would be pretty solid, but for “the Donald” would be considered losses. With no wins he will have reached a point that it would be hard for him to endlessly tout polls anymore - which is half his shtick (creating the aura of inevitability). I really don’t know if Trump could even stand to be in a race he wasn’t winning almost all these state contests.
Honestly, I don't know who will win NH, and I don't think anyone else knows either.
I suspect that Trump's support is a mile wide and an and inch deep there, meaning that there are lots of Independents who are supporting him now, but who are willing to switch, or who are willing to cross over and vote for Clinton in the Dem primary, if they think that Bernie is too dangerous. Not many, but some.
If Trump's marginal supporters (voters who want to pick a winner and don't think he can beat Clinton) decide to switch, I think they will go to Rubio.
Cruz has support from Evangelicals, and believe it or not, there are Evangelicals in NH. Cruze benefits from Santorum and Huckabee dropping out today. Sunday's sermons can drive voters to the polls for Cruz.
Cruz also benefits from his ability to organize his supporters. His ability to get his supporters in Iowa to the polls was impressive. If he has duplicated that in NH, that could be half the battle.
But, what do I know.