In the suit, the N.R.A. said that text messages and emails demonstrated that “another errant N.R.A. fiduciary, Chris Cox — once thought by some to be a likely successor for Mr. LaPierre — participated” in what was described as a conspiracy.

The court filing includes text exchanges in which Mr. Cox and a board member appear to be discussing an effort to oust Mr. LaPierre, though the full context is unclear. The N.R.A. is conducting an internal review of the matter, and a spokesman, Andrew Arulanandam, said on Thursday that Mr. Cox had “been placed on administrative leave.”

Mr. Cox, in a statement, said: “The allegations against me are offensive and patently false. For over 24 years I have been a loyal and effective leader in this organization. My efforts have always been focused on serving the members of the National Rifle Association, and I will continue to focus all of my energy on carrying out our core mission of defending the Second Amendment.”