Over the weekend former Pennsylvania Sen. Rick Santorum took to the pages of the Wall Street Journal to preview his tax reform plan, which is centered on a 20 percent flat tax for individuals and corporations:

A Flat Tax Is the Best Path to Prosperity

Since 2007, 15,000 American factories have shut down and more than two million manufacturing jobs have been lost. Wages have flatlined; American families are struggling.

In every recovery since 1960, real GDP grew by 4% a year, according …