I know something about this subject. Forty years ago, while working for New York Rep. Jack Kemp, I helped originate the Republican obsession with slashing taxes that came to be called “supply-side economics.” While I believe this theory played a useful role in economic theory and policy in the late 1970s and early 1980s, it has long outlived its usefulness and is now nothing but dogma completely divorced from reality.

. . .

Thus Republicans have long argued out of both sides of their mouths. On the one hand, they assert, without any evidence, that tax cuts pay for themselves by greatly expanding the economy, and that tax cuts will starve the beast and reduce spending. Thus in Kansas, the state hired Arthur Laffer, one of the original supply-siders, to say that tax cuts would pay for themselves. When taxes were slashed and revenues collapsed, the Republican governor and legislature sharply cut spending. It is Republican dogma that all deficits result from excessive spending, never from tax cuts.

Republicans believe that statutory rates of taxation are all-powerful, even though almost no one pays them; deductions, credits and exclusions reduce the effective tax rate (taxes divided by income) in many cases to zero. But the historical experience tells us this theory is nonsense. The Tax Reform Act of 1986 reduced the top personal income tax rate to just 28% from 50%, and the corporate tax rate to 34% from 46%. Yet there was no increase in the rate of economic growth in subsequent years and by 1990 the economy was in a deep recession.

Strenuous efforts by economists to find a growth effect from the 1986 act have failed to find any.There were accounting effects as income was shuffled around to take advantage of tax changes, but no rise in investment or any significant effect on labor supply. "The aggregate values of labor supply and saving apparently responded very little," economists Alan Auerbach and Joel Slemrod concluded in an authoritative study.

Virtually everything Republicans say about taxes today is a lie. Tax cuts and tax rate reductions will not pay for themselves; they never have. Republicans don’t even believe they will, they are just excuses to slash spending for the poor when revenues collapse and deficits rise. There is no evidence that tax reform raises growth, although it may improve fairness and tax administration. And the Republican idea that tax increases always crash the economy is belied by the experiences after Bill Clinton raised taxes in 1993 and Barack Obama did the same in 2013. The economy grew nicely and the stock market boomed in both cases.