You have to go back awhile!
The last time Democrats led a major, across-the-board federal income tax rate cut was with the
Revenue Act of 1964, passed under President Lyndon B. Johnson. This legislation, originally proposed by President John F. Kennedy, was a significant, across-the-board reduction: It lowered the top marginal income tax rate from 91% to 70%.It reduced the bottom individual income tax rate from 20% to 14%.It also cut the top corporate tax rate from 52% to 48%.
Amazingly, they still can't figure out why they don't get my vote 50 years later!