How Romney could fail to get enough delegates
Just to provide a sense of how this could happen, I spent some time playing around with CNNs delegate calculator feature and divided the states up two categories. Obviously, this is pretty rough. We dont have much polling data for these states, and the fact that Santorum could win Colorado means that Romney may not as strong in the mountain west as everybody once thought. Furthermore, theres also the possibility that both Santorum and Gingrich could fade before contests in other states take place.
With that said, here are the states that are probably solid or lean Romney states: Alaska, Hawaii, Washington, Oregon, California, Utah, Arizona, Idaho, Montana, Wyoming, New Mexico, Michigan, Maine, Vermont, Rhode Island, Massachusetts, Connecticut, New York, New Jersey, Delaware, Maryland, Virginia (where Santorum and Gingrich arent on the ballot), and Indiana (where Santorum isnt on the ballot).
Here are the states that its easier to see Santorum or Gingrich winning: Ohio, Pennsylvania, West Virginia, Kentucky, North Carolina, Georgia, Tennessee, Louisiana, Alabama, Arkansas, Mississippi, Wisconsin, Illinois, North Dakota, South Dakota, Nebraska, Kansas, Oklahoma, and Texas.
Because most states in 2012 are allocated proportionally rather than winner-take-all, its really difficult to predict how the delegates would be awarded. Romneys opponents will win delegates in states that he wins and hell get delegates in the states that he loses. But just for the sake of this exercise, if Romney were to win all of the delegates in all of the states that I identified above as solid or lean states, it would only get him to 1,008 delegates, according to the CNN calculator -- still short of the required 1,144.