They can help dispel stereotypes, as happened with Reagan and to some extent destroy stereotypes as happened with W Bush and the claim that he was "stupid".
They helped Clinton, Reagan and W, and they could make a difference here. If Romney comes across as plastic, he could lose ground, if he comes across as reasonable, likable, and decently smart, it will give him a boost.
Oh, and McCain was hurt by his appearance and incapacity to frame issues. It helped him lose.
I hope that you are right.
LLS
I think the debate(s) give Americans the chance to see Romney for themselves without ads and without the lamestream telling them about him “from their pinhead point of view.”