The MSM will predictably prop up a GOP candidate (e.g., Huckabee, Romney, Palin) who has electability issues (perceived or actual), with plans to then dump all over the candidate once he/she receives the nomination.
The problem with your theory is that they only give “favorable” press coverage to candidates that are unknown. Pawlenty, Santorum, and the Indiana boys will probably get lots of great press until they compete.
In other words, almost every candidate will get somewhat positive coverage until they are the inevitable.