Actually, it was Democrats who killed the 70% tax

It’s also worth remembering that the tax burden for most Americans was much higher in 1980 than it is today. For example, the middle quintile of Americans paid a federal tax rate of 19 percent in 1980, compared with 14 percent in 2015. Inflation was producing “bracket creep,” which meant that tax burdens were going up even while real wages were constant.

All this made the idea of across-the-board tax reductions popular, so much so that a strange dynamic developed. Congressional Democrats decided there was nothing to be gained from fighting Reagan’s tax cut, and they decided to propose a tax cut of their own. Over the next few months, Reagan and the Democrats presented dueling tax-cut bills, and they kept tweaking their bills to appeal to wavering members of Congress.

It was in this battle of the bills that the Democrats proposed to cut the top tax rate to 50 percent. They thought this would help attract votes from conservatives in both parties in the House. And importantly, they decided that in terms of revenue, the superhigh top tax bracket that draws so much political attention just didn’t mean very much: Of the $517 billion the Treasury collected in 1980, only $3 billion to $5 billion came from the 70 percent bracket — less than 1 percent of total tax revenue.