[Man50D]

What’s to keep them from just upping the rate like the states do?

The Fair Tax will be transparent since the hidden taxes will be eliminated and the Fair Tax rate will be a separate item on the receipt. If Congress were to attempt a tax hike people could see the raise and respond immediately. More importantly if the rate is raised too high then people will respond by reducing their purchases. Doing so would lessen the amount of taxes collected. It will force Congress to keep The Fair Tax within reasonable boundaries. Founding father and first Secretary Of The Treasury Alexander Hamilton stated this concept in his Federalist Paper #21. To quote:

It is a signal advantage of taxes on articles of consumption that they contain in their own nature a security against excess. They prescribe their own limit, which cannot be exceeded without defeating the end proposed-that is, an extension of the revenue. When applied to this object, the sayin is as just as it is witty that, "in political arithmetic, two and two do not always make four." If duties are too high, they lessen the consumption; the collection is eluded; and the product to the treasury is not so great as when they are confined within proper and moderate bounds. This forms a complete barrier against any material oppression of the citizens by taxes of this class, and is itself a natural limitation of the power of imposing them.

[Paladin2]

"If Congress were to attempt a tax hike people could see the raise and respond immediately"

Objection!

Sustained.

The 'rats in control couldn't care less.