https://supreme.justia.com/cases/federal/us/408/501/#tab-opinion-1949845
“....it has never been seriously contended that these political matters, however appropriate, have the protection afforded by the Speech or Debate Clause.
Careful examination of the decided cases reveals that the Court has regarded the protection as reaching only those things "generally done in a session of the House by one of its members in relation to the business before it," Kilbourn v. Thompson, supra, at 103 U. S. 204, or things "said or done by him, as a representative, in the exercise of the functions of that office," Coffin v. Coffin, 4 Mass. 1, 27 (1808).