Some fear the Senator waited too long to attack Obama over Ayers, say the issue doesn’t connect with voters.

Gingrich: “He has to make the case that he’s different than Bush and better than Obama on the economy. If he doesn’t win that case, it’s all over….”

GOP strategist Castellanos: “He doesn’t need an attack strategy, he needs a comeback strategy.”

Plus: Gingrich says he “can’t defend” McCain’s mortgage proposal.