LOS ANGELES — A pitched leadership battle is taking place inside one of the country’s oldest neo-Nazi groups. On one side, a true believer is pushing to attract new members and expand the ranks. On the other, a black former Baptist preacher is hoping to destroy the hate-spewing group from the inside.

James Hart Stern, the 55-year-old preacher from Los Angeles, took control of the group, the National Socialist Movement, in January. He is now struggling with Burt Colucci, 43, a longtime member, over leadership of the group. The fight has thrown the organization into upheaval during a time when far-right extremism is on the rise and other white supremacy groups are gaining ground.

The two men are fighting over who has control over the group’s official website. That site is now more important than ever, as more hate groups recruit with memes than marches. The N.S.M., as the group is known, has struggled to keep up as its membership dwindles.

The bizarre and twisting tale of how the battle came to be involves an unlikely prison friendship, lawsuits and even a team of Hollywood producers.