His favorability is underwater:
To win in November, Romney will have to make history. Not by being one of the wealthiest men elected president, or even the first Mormon, but by changing more minds that are more deeply set against him than any other nominee in recent memory. If he can’t convince the unprecedented number of voters who have already decided they don’t like him that, actually, they do, he will be heading back to Massachusetts—or New Hampshire, or California, or Utah—come November 6.
And his share of the primary vote is below historical precedents:
One of Mitt Romney’s basic arguments these days is that he is well ahead of his Republican presidential rivals in both the number of delegates and popular votes won. That is true. But if he goes on to win his party’s nomination, it is likely to be with the lowest share of the nationwide GOP primary vote since the era of the primary-dominated nominating process began in the 1970s.