MADISON, Wis. — U.S. Senate candidate Leah Vukmir is calling on her Republican opponent Kevin Nicholson to disavow former White House strategist Steve Bannon over comments attributed to him in a new book.

According to excerpts of Michael Wolff’s book released Wednesday, Bannon thought Trump’s son’s contact with a Russian lawyer during the campaign was “treasonous” and “unpatriotic.”

Jess Ward, Vukmir’s campaign manager, calls Bannon’s comments a “vicious attack” against the president and his family. She says that combined with Bannon’s endorsement of losing Alabama Senate candidate Roy Moore should lead “any self-respecting Republican” to question his role in the party.

Nicholson spokesman Brandon Moody rejected Vukmir’s call, saying it was “disappointing” Vukmir would attack Nicholson for an endorsement that she “aggressively sought.” Moody says it’s easy to see why Vukmir would be frustrated.