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1.
A term to describe groups of hardworking employees, particularly those working in the legislative realm. This is a play on the use of the term "caucus" to reference other legislative subgroups, such as the Legislative Black Caucus, Latino Caucus, Education Caucus, or Downstate Caucus.
Legislative Staffer A: Are you ready to go home yet?

Legislative Staffer B: Not yet. The midnight caucus isn't quite ready to adjourn.
by Springfield Staffer February 24, 2010