Progressive tax systems have tiered tax rates that charge higher income individuals higher percentages of their income and offer the lowest rates to those with the lowest incomes. Flat tax plans generally assign one tax rate to all taxpayers. ... A flat tax would ignore the differences between rich and poor taxpayers.
If someone is making little money but everyone has to pay the same taxes it will not be good because he or she will have a hard time with the flat tax, while the progressive tax grows with you or shrinks with you in your life time, so if you are making little money you will be paying very little.
The political party will take control and make things the way they want it causing a big hole in power making it so that that political power almost controls more than any other political party. Conclusion it would not be good