This could really be effective.
Newt can go completely negative on Romney, freeing Santorum to point out how the GOP needs to band together to fight Obama (without having to go negative on any GOP candidate).
This gets rid of the RINO while pulling the GOP together. It may just save the GOP.
If this is what Gingrich has in mind (to fall on the grenade for Santorum) then I have just raised my opinion of Newt.
In your scenario then Gingrich could become Secretary of State like Hillary did for Obama.