I’m thinking perhaps the best way to keep Romney out is for Newt to stay in all events with proportional delegate allocation. However, in winner take all states, I think Newt should throw in with Santorum and try to beat Romney in those states.
At this point in the race if the Newt supporters want Newt to be on a winning team and still see Newt still in the race is for Newt to team up with Rick Santorum as his running mate to try to stop Romney from getting the nomination.