Larison tries to understand Mitt's rationale:
It’s tempting to say that he has reinvented himself so thoroughly that he can no longer remember what is true and what isn’t, and he has absorbed and appropriated so many new positions over the years that it all gets jumbled together and re-mixed according to whatever the political need of the moment happens to be. It’s easy to lose track after the fourth or fifth incarnation. More likely, he is so contemptuous of the people he tells these lies to that he never thinks he will be found out.
Steve Benen adds:
Romney and his team have demonstrated a willingness to lie — blatantly and shamelessly — with discomforting ease. We’ve seen this in offensive campaign ads, routine talking points, policy arguments, and even personal anecdotes and characteristics. And when pressed, Romney and his aides have freely admitted, more than once, that niceties such as facts, evidence, and reason just aren’t that important to them. Dishonest “propaganda” should simply be expected and accepted, they’ve said.
Krugman goes further:
[W]ith all the bad things that have happened in American politics over the centuries, I can’t think of any candidate who has lied so freely, with so little compunction.