Historical clue formulations

• Philosopher who wrote "The bureaucracy is a circle from which no one can escape" — 2025-07-06
• Karl who co-wrote a manifesto — 2020-10-26
• His tombstone reads "Workers of all lands unite" — 2020-08-02
• Influence on Castro and Mao — 2019-01-20
• "Das Kapital" author — 2018-10-03
• See 10-Down — 2018-07-24
• Who said "Revolutions are the locomotives of history" — 2018-01-06
• Who said religion "is the opium of the people" — 2017-09-06
• Who said "Revolutions are the locomotives of history" — 2016-10-30
• Funny Groucho or Harpo — 2016-05-30
• Who said history repeats itself "the first time as tragedy, the second time as farce" — 2015-12-25
• Harpo, Zeppo or Groucho — 2015-02-16
• Karl, Richard or Harpo — 2014-10-21
• Richard with the 1989 #1 hit "Right Here Waiting" — 2013-03-21
• "I have had a perfectly wonderful evening, but this wasn't it" speaker — 2012-10-26
• Groucho or Chico — 2012-07-17
• Karl with a manifesto — 2011-04-11
• "The Poverty of Philosophy" author — 2011-01-14
• Any brother in "Animal Crackers" — 2010-04-19
• Last name in comedy — 2009-01-08
• With 53-Across, noted comedy group, in brief — 2007-07-25
• Karl who philosophized about class struggle — 2006-09-11
• Philosopher who gave his name to an -ism — 2006-08-10
• Manifesto writer — 2002-06-15
• Out-of-favor icon — 2001-10-28
• "Manifesto" writer — 1998-04-07
• Zeppo, for one — 1997-03-12
• "Capital" fellow — 1996-10-20
• Groucho or Zeppo — 1996-09-16
• Communist Karl — 1996-01-01
• Pop singer Richard — 1995-08-24
• "Das Kapital" author — 1995-04-30