I like Cain a lot.
But enabling a federal income tax and a federal sales tax at the same time is very, very bad.
To implement a federal sales tax, first an amendment to the USC must be passed stating that the federal government can never have both taxes at the same time.
Otherwise, they will just continue to jack up both rates until we’re paying 25% on both, or 50% total.
Cain should know better.
I don't think you need an amendment. If you repeal income tax in the same statute you pass a sales tax in, then you would need a whole new bill to start up the income tax again. That would mean it would need to pass the house, and have a filibuster proof majority in the Senate, and have the President sign it. That's different than just changing rates that they can do in budget reconcillation to avoid a filibuster.
That was a chief component of the Fair Tax - it had a constitutional amendment repealing the 16th amendment, in effect, making income taxes unconstitutional,
whose ratification was a pre-requisite for implementing the NRST.