The Ezra Kleinless wonkblog remains excellent. In particular Matt O’Brien is about as young, smart, witty, and hard working as Klein. However, I think he may not have read everything.
He notes that the allegedly reformicon tax plan includes the Bush tax cuts for the rich on steroids. Then he reviews recent, but only recent, history writing
Why yes it is (pretty much).
Point 2 of the 10 point plan in the Communist Manifesto
Now 39.5% would seem absurdly light to Dwight (Eisenhower) but it would have sounded extremely heavy in 1848*. Note that Marx and Engels added “or graduated” in case their readers needed further explanation of the strange concept of a “progressive income tax.” At the time, a flat income tax would have been less regressive than the existing systems based mainly on excise taxes.
* typo corrected thanks to Lyle in comments.