Newt or the Huckster could certainly wipe the floor with Obama during a debate any day.
Gingrich and Huckabee may be good debaters, but it is unrealistic to say that they would wipe the floor with Obama.
Obama is super intelligent, can be most charming, and is one of the most effective speakers, possibly debaters, in public life today.
No one wipes the floor with Obama.
This, pretty much.
In terms of "winning" a Presidential debate, haven't most of the winners come off as amiable, knowledgable, and calm and collected? Basically, it seems that the most important strategy is to 1) not come off as abrasive or cold (see: Gore, Al and Nixon, Richard), 2) display knowledge of current issues and set forth a semi-clear agenda, and 3) not screw up (see: Dukakis, Michael and Ford, Gerald). If one is looking to deliver the proverbial "Kill Shot" during the debates, I just don't see that happening. It's not likely that anybody will look much better than Obama (who doesn't look all that different from JFK in that setting) in a debate format--at least not to the point that voters will change their minds based on the debate performance.