Obama and his administration could have tried to make the case that his statement "If you like your plan, you can keep it." wasn't a lie.
Unfortunately, the self-proclaimed neutral watchdog Politifact (in reality, they're probably a little left-leaning) named it the lie of the year.
It's not just that his statement was false, but he deliberately used a false statement to make sure this reform passed. If he hadn't it would have been even more difficult than it was.