Both the house and senate versions of the Streamlined Sales bill have larger cosponsor list than the Fair Tax bills. I make the assumption that this is because they have a larger (state sponsored?) organization pushing their bill.
Since both groups seek a federal sales tax, my overall question is "Is there an opportunity to combine forces?"
But my immediate question is "When a state government does 'harmonize' its tax system with the Fair Tax, does the state then have the opportunity to collect a state tax along with the federal tax on sales and services that cross state lines?"