The funniest part of Rick Perry’s flat tax plan is that he spends a lot of time and effort describing what a horrible, confiscatory, inferior system the current US tax code is – and then says if you like it, you can keep it.

The folks in Washington might not like to hear it, but the plain truth is the U.S. government spends too much. Taxes are too high, too complex, and too riddled with special interest loopholes. And our expensive entitlement system is unsustainable in the long run [...]

The plan starts with giving Americans a choice between a new, flat tax rate of 20% or their current income tax rate. The new flat tax preserves mortgage interest, charitable and state and local tax exemptions for families earning less than $500,000 annually, and it increases the standard deduction to $12,500 for individuals and dependents.

So the tax code is riddled with loopholes, all of which we’re going to keep, in case people opt for the old system. It’s unsustainable, and here to stay. It’s too long, so we’re going to add pages to it with this flat tax option.

In the same breath, Perry says that dozens of “carve-outs” will be eliminated, so it may be that you’d just have the option of your current rate of tax or a 20% rate. In that case, this would be a flatter but not flat tax, since rates between 0-$34,800 are currently below 20%.

It’s a 20-20 plan, too, because the corporate tax rate goes down to 20%. It also eliminates the estate tax, the dividends tax, the capital gains tax, and the income tax on Social Security benefits for people who continue to work while they collect. Then there’s a spending cap, but not at 20% of GDP, which is where it was before the financial crisis in 2007, but at 18%, a 10% reduction from 2007 levels with an older population. And there’s a balanced budget amendment to the Constitution to lock all this in.

It’s basically Cut, Cap and Balance with a flat tax added, for the conservative quinella. Rick Perry is flailing around (including going full birther), but having a plan that he can point to might help him. More important is the dynamic of the flat tax becoming a GOP litmus test, along with Cut, Cap and Balance, which Mitt Romney has already endorsed. Flat tax plans are full-on Monets; OK from afar but devastatingly bad for most Americans in the details. So if conservatives want to pick that hill to die on, I say good luck with it.