As for Huckabee and Santorum, combined they got only 2.8%. Simple math suggests that Rand supporters are much more important than Santorum and Hucks, because there are a lot more of them. As to where they will go: I think Rubio. Not sure why I think that, but I do.
Because Rand Paul voters are the least likely to actually show up and vote for anybody else.
If RCP averages hold (and they failed in Iowa, to be sure) here's the order they finish in:
Trump
Cruz
Kasich
Rubio
Bush
Christie
Fiorina
Carson
I would say that Christie and Fiorina logically should quit at that point. Christie has a day job to go back to, should be easy for him.
Carson might want to hold on for a state with a larger black population, like South Carolina, but certainly could bow out after a humiliating last place finish in New Hampshire.
One would think that Bush finishing 5th in New Hampshire after finishing 6th in Iowa should be enough to finish him off, but I suspect he goes on South Carolina too.
I think anyone who has scored a win, place, or show in either of the first two contests sticks around: Trump, Cruz, Rubio, Kasich would, by this logic, remain semi-plausible candidates, and move on to South Carolina.
The large field has caused a slower than usual winnowing effect this year.
Cruz, Kasich, Rubio and Bush are clustered within +or- 1% OF 10.8%. Were the voters who went for Rand, Huck or Santorum to move decisively towards one of the tied-for-second crowd it would be a game changer. Rand had the most supporters of them in New Hampshire.
Bush seems least likely to get Rand voters. Kasich less so. I think Cruz and Rubio both have a good shot at picking them up. Cruz and Rand were buddies in the Senate before the campaign, and have a similar "insurgent in the Senate" backstory. Rubio's personality, somewhat happy and disarming, is more like Rands. It's hard for me to imagine Rand voters going to Trump, but they are both rebels, though Rand himself seems to really dislike Trump.