From The New York Times' Nate Silver:

Adding up the projections from the ten states, I show Mr. Romney getting 217 delegates, or almost exactly half of the total available. Mr. Santorum would get 107 delegates by these projections — about a quarter of the total — with Mr. Gingrich getting 61 and Mr. Paul 25.

There is, obviously, a lot of uncertainty in these numbers — especially since the delegate math is somewhat non-linear as when candidates fall just above or below a qualifying or majority threshold. But Mr. Romney has the makings of a strong evening, and one that could put some further distance between himself and his rivals.