The community, known as “The Marty Army,” began as a fan chat for the “Halo” video game series. O’Donnell later moved it to Discord, where he and moderators he selected oversee the group. His campaign website links to the forum, and he promoted it to supporters after announcing his first congressional run in 2024.

Most discussions focus on gaming, but the review found offensive remarks appearing in conversations about politics, current events and games. In one May 2022 exchange, users reacted to a post supporting O’Donnell by spelling racial slurs with letter emojis. In a January 2025 discussion about free speech, a member said they wanted to use a racial slur but held back because it would attract the kind of attention O’Donnell did not want.

Two former members said users sometimes relied on coded language because they believed more explicit racist comments would draw moderator scrutiny. One, Deacon Dameron, said he was removed from the group after calling another user a “dork.” He described the pro-slavery sentiment he saw as widespread, rather than limited to a few members.

The review also found posts expressing sympathy for Nazi Germany. In March 2024, one user said the Nazis had done some positive things that were eclipsed by their crimes. Another asked whether Adolf Hitler was evil, adding, “aside from the Holocaust.” A separate post in February read, “Heil Hitler.” Some users with Nazi sympathies were removed, but posts remained visible, according to the review.

O’Donnell has said he rejects fascism and has repeatedly pledged to ban racist and antisemitic users. In the spring, he warned the forum that anyone showing “even a hint of antisemitism” would be banned immediately. Users responded with an emoji depicting an exaggerated nose and the word “goy,” a term for a non-Jew that can be used disparagingly. Wendy Melillo, an American University journalism professor who studies extremist chat rooms, described those comments as coded antisemitic hate speech. She said the “Heil Hitler” post was explicit, not coded.

O’Donnell’s campaign said he has no tolerance for hate and began assigning a staff member to monitor the forum after becoming aware of the issue in the spring. Campaign spokesman Keith Schipper said nearly 200 users had been banned for hateful rhetoric, including many identified in the review, while acknowledging that some posts had been missed over the years. Schipper said O’Donnell supports Israel and opposes antisemitism and bigotry.

The campaign also disputed the significance of a photo O’Donnell shared of himself wearing what he had called a Mussolini mask. Schipper said the mask was bought as part of a scary Halloween costume nearly two decades ago and was not sold or worn as a deliberate portrayal of the Italian dictator.

O’Donnell has also said he had not realized antisemitism was resurgent. In a September interview, he said he had thought it was no longer a concern, then suggested it had been present beneath the surface. The remarks followed a report that O’Donnell had hosted far-right influencer Charles Cornish-Dale, who has expressed Nazi sympathies, on his podcast.

O’Donnell is challenging four-term Democratic Rep. Susie Lee in the Nov. 3 election. President Donald Trump has endorsed him. The race is among those that could affect control of the narrowly divided House, though Republicans recently reduced spending in several congressional contests, including O’Donnell’s.