An extraordinary backstage confrontation between Donald J. Trump’s campaign and the staff of the Presidential Commission on Debates unfolded just minutes before the debate on Sunday night after Mr. Trump tried to give seats in his V.I.P. box to a group of women who have accused former President Bill Clinton of making unwanted sexual advances.

The situation de-escalated only after the commission threatened to call security to remove the women if they tried to sit in the box, where they would have been right next to Mr. Clinton and in Hillary Clinton’s line of sight from the stage — a spectacle that Mr. Trump and his top advisers tried to engineer for maximum shock effect just as tens of millions of people would be tuning in from around the world.

With little other option to avoid a physical scuffle, however, the Trump campaign relented.

The episode was the latest in a string of threats, taunts and gamesmanship over the debates from both campaigns.

The incident in St. Louis on Sunday night, reported earlier by The Washington Post, rose to the highest levels of the Trump campaign and the debate commission. Moments before the kerfuffle over seating, Mr. Trump and his campaign chief executive, Stephen K. Bannon, had surprised reporters by staging an impromptu news conference with the Republican nominee and three women who have claimed that Mr. and Mrs. Clinton minimized and belittled their claims of sexual misconduct. Among them were Paula Jones, whose sexual harassment lawsuit against Mr. Clinton helped force his impeachment, and Juanita Broaddrick, who has accused the former president of raping her in 1978. A fourth woman, who said she was raped as a child by a man Hillary Clinton defended at trial in 1975, also appeared at the impromptu panel.