the current senate bill adds $1.4 trillion to the deficit over ten years. the gop says economic growth will pay for the plan eventually but senator bob corker among others worry that might not happen. he wants to include a provision to raise taxes if revenue falls short. so far independent estimates show the bill does not hit the gop's aggressive growth targets. let's bring in julian zelizer. good morning again. >>reporter: good morning. >> when you look at who has expressed concerns and who the wild cards are, and the kinds of things that are packed in here, do you repeal the original mandate of obama care. the president says it is a middle tax cut. this is a hard sell. >> you can't resolve all of these concerns. it's almost impossible.