Romney response ad: "The only person I will ever like firing is Barack Obama."
Why will it be successful? Because 50-60% of the country wants to fire Barack Obama.
Another good Super PAC ad: The 2008 Barack Obama "Hope" painting with "Hope?" below it that eventually morphs into "Nope." Just have a narrator who simply asks "Hope?" and then says, "Nope." I guarantee it will be brutally effective, especially considering the scorched earth campaign Team Obama is apparently intent on running.
That doesn't really make any sense, since Romney can't fire the President, only the voters as a whole can and such an ad would be completely ridiculous.
Ad-hominem attacks will fall flat against the facts of Romney's record.