Nate Silver looks at the data to see how Santorum would have fared without Newt in the race so far. Bottom line:
Mr. Santorum would have carried four states that he actually lost.
But the delegate hill would still be steep. Nonetheless, it seems to me that the best way for Newt to exact revenge on Romney – and do his party a service – would be to withdraw now and endorse Santorum. If the GOP is going to nominate Romney, it shouldn't be by default.