It's practically everything. And it started from the day he announced his candidacy, when he claimed Obama had made the economy worse (and then claimed he hadn't said it).
Romney's vacillations have of course earned him Etch-A-Sketch status (from his own spokesperson, remember), but with the way he lies, persistently, and with volition and understanding (remember, he approves his ads), you can't possibly believe that someone with such a mendacious record will be good for America. And neither does he, or he wouldn't feel like he needs to lie about Obama in order to persuade you of his superiority.