Honestly? I think some Christians and conservatives are worried about Trump. His personality can be off putting. They were looking at Carson as an alternative. Now that more is known about Carson, will they shift back to Trump, move to Cruz, or go somewhere else? That remains to be seen.
They will split between Cruz and the full-on amnesty candidate (Rubio?).
As a result, Cruz will win Iowa handily, then fade out of the race after the March 1st primaries.