Despite what her "right-to-be-wrongness" Ann Coulter says about Mitt's inevitability, Republicans--if they are smart--should always elect the man for nomination who wins Ohio. Because in the general election, it is the best indicator of who will be President.
Santorum has thicker skin than Newt and Mitt combined, and next to Newt, he's the best debater left in the bunch. But most importantly he is the sharpest contrast to Obama--in nearly every imaginable category.
Newt is steadily polling at 14% in the polls. Santorum has exploded in Michigan and Ohio, is nearly within the margin of error to Romney in Arizona, and almost the same within Gingrich in Georgia. Meanwhile in some states Gingrich finishes last, Santorum never does. But if you add 2/3's of Newt's total to Santorum's, Rick Rollin' would become the new GOP past time.
If Gingrich is a man of principal, he will allow the consolidation and much-more-baggage-free candidacy of Rick Santorum to zoom into an even further all-out lead nationally. If Gingrich stays in, it is obvious his feelings about Romney's danger and likely losing proposition as nominee will come true. And the former speaker would have only himself to blame.
If Romney is the nominee, Obama will be President for a second term. (His inability to take Obama on--on his biggest weaknesses, the target of his faith's racially questionable history and the twisted way the mainstream media will exploit that, his inability to not say things from an entirely silver spoon perspective, and his lack of distinction from Obama on many social issues--like subsidizing abortion, and creating "gay" marriage.)
The GOP's job at the moment is to pick the best candidate they can to beat Obama, and the one who is most-different-than him presents the best possibility.
Especially if that candidate wins Ohio.