Now the N.R.A., which has faced two years of turmoil and infighting, is confronting a new adversary from within its own senior ranks.

Josh Powell, one of the group's highest-ranking former executives, is poised to release "Inside the NRA: A Tell-All Account of Corruption, Greed and Paranoia Within the Most Powerful Political Group in America." Mr. Powell, former chief of staff to Wayne LaPierre, the group's longtime chief executive, says the N.R.A. is "rife with fraud and corruption" and writes that its finances "are in shambles," and that "it has operated in the red for the past three years, despite annual revenues of roughly $350 million."

The book, to be published Sept. 8 by Twelve, a division of Hachette Book Group, will arrive as Mr. LaPierre and the N.R.A. are fighting for their survival.

Both Mr. LaPierre and Mr. Powell, who for a time was seen as the N.R.A.'s de facto second-in-command, are named defendants in the suit brought by the attorney general, Letitia James, who has special jurisdiction because the N.R.A. was founded in New York.