You're Doing It Wrong
How should the Romney campaign push back against the ad accusing Romney of killing some guy's wife? Not like this.
“To that point, if people had been in Massachusetts, under Governor Romney’s health care plan, they would have had health care,” Andrea Saul, Romney’s campaign press secretary, said during an appearance on Fox News. “There are a lot of people losing their jobs and losing their health care in President [Barack] Obama’s economy.”
No no no. First destroy the ad's credibility, which has largely been done, and make Obama answer for the group that produced the ad. Then, note that under Obama's plan, the man who lost his health care because he lost his job would face a fine under Obama's plan if he didn't go out and buy health insurance. Faced with his wife's cancer, the man would find himself in the loving embrace of the IRS, which now enforces the ObamaCare mandate. That's what Dr. Obama would do for you, too!
Keep the heat on Obama for a) sanctioning lies (point out that that super PAC hasn't gotten the Cory Booker treatment, so its message must have been authorized by the Obama campaign) and for b) forcing a terrible and unpopular health care plan against the will of the American people that would only have made the man's problem worse.