When Mitt Romney started his 2012 campaign, he basically assumed that all he had to do to win was point out to people that the economy was in the toilet. As it turns out, the voters already knew that and before giving him the keys to the White House, they want to know how he is going to fix the economy. Since he doesn't want to discuss his economic plan in any detail other than "tax cuts" and seems to be falling farther and farther behind, he is now considering broadening his attacks, hitting President Obama on energy, health care, taxes, and spending. Note that what he is talking about doing is more attacking. He is not planning to tell people why they should vote for him, just why they should not vote for Obama. For whatever reason, he can't get out of attack mode. The problem with that approach so far is that although he may convince people that Obama is far from perfect, he hasn't even tried to make the case that he is better.
Traditionally, re-election campaigns are about giving the incumbent either a passing or failing grade, and Romney still seems convinced that if people judge Obama a failure, they will vote for him by default. What he seems to have missed is that he is viewed in a very unfavorable light with an approve/disapprove rating under water. Relentless attacks on Obama without explaining why he is a better alternative don't seem to be doing the job for him, but he keeps trying.