Way too scripted, actually entirely scripted. The problem is Ali G isn't the kind of character to be scripted. He works best in more ad hoc situations, like interviews on talk show television. The movie has a few "smart" jabs here and there, but for the most part is a tiresome lowbrow hyper-immature comedy.
Would have been a million times better if it was actually about him infiltrating or messing with actual real politicians-rather than the absurdly stupid fictional plot he is forced into here.