The FairTax leaves in place excise taxes, like the federal gas tax. Its not hard to imagine that, from a politician's point of view, raising those taxes would be the way to sneak in tax increases without touching the NRST rate.
For instance, the gas tax is now 18 cents; the FairTax would tax the gas tax at 30%, so increasing the gas tax would automatically increase the amount of sales tax collected on a gallon of gas without increasing the FairTax rate.
First of all the FairTax does NOT tax the gas tax.
You need to sharpen a whole of thinking before you can join in at this level.
Even allowing for your error correction, the FairTax administers the gas tax which is earmarked for roads and bridges. Any increase in gas tax is completely constitutional as they are necessary for roads and bridges. It has nothing to do with 'sneaking' which is typical of your thinking.