Here it is — the letter written by Honorable Walter B. Jones to Honorable Cathy McMorris Rodgers Oct 6, 2015 writing that

With all the voter distrust felt around the country, I’m asking that any candidate for Speaker of the House . . . withdraw himself from leadership election if there are any misdeeds he has committed since joining Congress that will embarrass himself, the Republican Conference, and the House of Representatives if they become public.”

This letter, naturally, became public immediately, and Kevin McCarthy stepped out of the Speaker of the House race.