The canditates of the two big parties aren't much different from each other, Obama is only slightly more 'liberal' than the other hopefuls but by no means any kind of radical, and if he was, he'd still have to have the backing of congress, as mentioned.
Nothing much will change, or the candidates wouldn't be endorsed in the first place and receive all that campaign money from the same folks and corps who donate to candidates from all sides.
Do you want Fanta Green or Fanta Red is the choice here, no milk, juice or coffee on the menu.
This is not 'democracy'.