the political divide say trump's rejiggering of the way the irs does business will cost 1,000 times what trump says is his fortune, in other words, it will cost the nation $10 trillion. cnn chief political correspondent dana bash is here what happen does the trump campaign have to say about these assessments? >> donald trump is saying that his plan is terrific, critics are wrong and don't know what they're talking about. we still don't have all of the specifics which allows opponents to dismiss his tax proposal as fantasy. >> reporter: if there's anything donald trump knows how to do, it's sell. and now, it's all about selling his new tax plan. >> the economy's going to just be absolutely like a rocket. it's going to go up. this is my prediction. this is what i'm good at. this is my wheelhouse. >> reporter: as much as trump is trying to build up his proposal, where nearly half of americans would pay no federal income tax, his rivals are urging voters to compare it to the alternatives. >> i caution people is to