Well two of the biggest tax cuts in the modern era were done by Democrats JKF and Carter..
It's frequently entertaining to see just what lies the Democrats will come up with to try to explain away their monstrous defeats.
In this case it's a truth combines with a lie. JFK did put a big tax cut into place. But Carter did little tax cutting... and sat back while inflation drove people incomes AND EXPENSES hugely higher. On paper this was a wash - they had more money, but everything cost more.
Except it drove many people INTO THE NEXT HIGHER TAX BRACKET... and there was nothing to balance this loss to their pocketbooks. So the Carter years wound up as a net loss, since many people were paying higher percentages of their incomes in taxes.
One of the things Reagan did, was to index tax rates to inflation, thus eliminating these "automatic" inflation-driven tax increases.