I contend that's not likely. If they were the type of voter that would vote for Santorum they would already be with him.
I believe if Romney's delegates abandon him they will go with the other anti-Santorum delegates in the Gingrich camp.
Everyone likes to talk about the anti-Romney vote. There's is a anti-Santorum vote that is at least as large.
I guess by that standard the anti-Gingrich vote is only surpassed by the anti-Paul vote. :)