Sens. Ted Cruz and Marco Rubio keep mixing it up on the merits of a flat tax. ‎Cruz wants one, and Rubio says it will lead to higher rates later and make America look like Europe. A Rubio super PAC disingenuously slams the Cruz flat tax as “a Canadian-style tax.”

There are many versions of a flat tax. Arthur Laffer and I helped Cruz as well as Sen. Rand Paul on their plans, which is modeled after a plan we outlined in our book called Return to Prosperity. But to say that a flat tax is dangerous is a dangerous claim. Don't we want low rates and a broad base with a simple return? Can anyone honestly believe that the Paul or Cruz plan would not generate huge growth with tax rates of 16 percent or less?

What's disturbing about the fatuous attacks by the Rubio campaign is that the Rubio tax plan leaves tax rates at 35 percent on individuals. That's even higher than what Rubio says the flat tax may rise to: 30 percent.

People should examine the tax plans side by side and see which one they like the best. They can do so here at the Leadership Project for America Foundation website. But Rubio's attacks against the flat tax are a setback for the conservative movement and will only help Hillary Clinton, Bernie Sanders, and other liberals block tax reform in 2017.