Probably not. First of all, Obama has never won a debate, so proudly saying he'd win the debate is pretty arrogant, and second, I bet the third party's numbers would increase slightly simply because they would get some exposure. Their ideas may sound appealing to some people. They really can't go any lower than they already are.
I disagree; I think Obama is able to beat McCain, and with Barr polling at 6% right now, he can sink pretty far. Once people see how nutty his ideas are, they'll back off, leaving only the former Paul supporters.
I went and read Barr website, some of the things on their aren't that bad, I would vote for Barr before McCain.