Trump v Carson

[Mehmentum]

I'm not certain that Trump needs to attack Carson.  While Carson does lead Trump in head to heads, I don't think the race could ever come down to a head to head between Carson and Trump. 

Suppose Carson wins Iowa and Trump wins New Hampshire, does that mean every other candidate drops out?  No.  It will be a messy process, but I think that one establishment candidate emerges as the consensus to save the GOP from the 'barbarians'.

In this scenario, a brokered convention becomes quite likely.  Trump will want to have a cordial relationship with Carson and his supporters for the convention.  Fighting with Carson would also be counterproductive, because it would play into the hands of the third candidate.

[Mehmentum]

Carson is likely going to be this cycle's evangelical candidate.  Both Santorum and Huckabee got 20.43% of the primary vote (exactly, in fact).  Carson, if he sticks around, will get about that much as well.  The reason why he polls higher than that in the head to heads is that all of the 'anybody-but-Trump' people are voting for Carson.

I think its very unlikely that the contest will narrow down to only Carson and Trump.  There's bound to be an establishment candidate in there somewhere.