This is an example not actual numbers of why a flat tax is not very good for most Americans. Its particularly true today when income disparity is so high and its the middle and lower income groups not elites who really are struggling.

I earn 100,000. I have to have 30,000 of that to pay my neccessities (things like food, clothing, housing, power etc you need to survive). I have 70,000 left which is not required essentially this is fat. I pay a 20 percent flat tax (the last estimate I saw said that to generate the same revenue as the income tax the flat tax rate would be about 23 percent but this is easier to do the math on for my example). SO I pay 20,000 in taxes have 50,000 in discretionary spending left.

Now I earn 25,000 which is close to the median. In reality virtually everything there is non-discretionary for most families but for sake of observation we will say they have 2,000 in discretionary income after the absolute neccessities are taken care of. I have 2,000 in discretionary income. I pay 5,000 in a flat tax. Not only is all my discretionary income gone, part of my income for neccessities is gone as well.

A flat tax would flatten many Americans and signficantly shift the tax burden from those most able to pay it, to those that are least able to pay it. This would occur even as disparity is at the highest point since the early 1900's and when much of the US public (but not elites) are just hanging on by their fingertips.

If they want to make the system fairer they can simple get rid of the deductions and stll have a progressive system.