When political campaigns falter, they tend to turn into circular firing squads. That appears to be the case today, with unnamed Romney "advisers" blaming top strategist Stuart Stevens for the former governor's desurging campaign.
I think Romney's problems are largely his own -- his own personality, his own preferred campaign style, and his own policy judgments. A political consultant I know and respect suggests that the campaign's failure to introduce and humanize Romney to the electorate during the summer, when the Obama campaign was painting him as a vulture capitalist, was a major strategic mistake, and probably doe at the insistence of the candidate -- as was his avoidance of discussion of his religious faith and activities.
His campaign style and policy emphases also reflect the "tin ear" that dooms many politicians. Joshua Green has a good piece arguing that Romney's approach is just what a bloodless CEO would do, rather than what a seasoned politician would do. I find that persuasive as well.
Both Romney and Obama seem to be introverts; both have access to the best and the brightest political advisers in their respective parties; but only one seems to have learned how to be themselves and still run effective campaigns.