I seem to remember Income Taxes being ruled unconstitutional by the Supreme Court in the late 1890’s. So how did they fix the problem? They made it constitutional.
Yes it took 52 years to make it legal. It was ruled illegal (unconstitutional) in many cases from 1861 to 1913. Progresives or Populists kept trying various income tax without apportionment schemes and were always shot down.
Here is a simple small view of history (short easy reading FR post) on the subject:
http://www.freerepublic.com/focus/news/2466444/posts?page=23#15
Take a quick peek at the link info in post #26 here.
As to why it was made constitutional? Jealousy. The old excise system had a built-in bias against small farmers.
But they got the solution completely wrong just as Obamacare is completely wrong as a solution to Healthcare access and affordability problems.
The question I asked in my research is why if the FairTax is so awsomely superior and in conformance with the visions of the Founders, then why didn’t the Congress of 1913 pass a FairTax? The answer is spelled out in the latter half of the link in post #26.