Boris Epshteyn, who oversees Donald J. Trump’s sprawling legal team, pleaded not guilty to nine felony charges on Tuesday in Arizona’s election interference case, highlighting the legal risks for the advisers and allies who attempted to keep Mr. Trump in power after he lost the 2020 presidential election.

Mr. Epshteyn has held onto his baseless assertions that the election was stolen and has not wavered in his support for Mr. Trump. By contrast, he was arraigned on Tuesday along with Jenna Ellis, a lawyer and Trump adviser who was among the former president’s staunchest defenders after the 2020 election, but who has since expressed regret.

Mr. Epshteyn appeared by telephone, and his attorney, Michael Bailey, pleaded not guilty on his behalf in a courtroom in Phoenix.

An attorney for Ms. Ellis also pleaded not guilty on her behalf on Tuesday. Ms. Ellis, appearing on a video screen, stated her name and date of birth and nodded slightly as the judge read her a standard list of admonishments that she not contact any victims, witnesses or co-defendants in the case.

Ms. Ellis pleaded guilty to a felony last year, in a similar case in Georgia. When she entered her plea in an Atlanta courtroom, a tearful Ms. Ellis said, “If I knew then what I know now, I would have declined to represent Donald Trump in these postelection challenges.” She added, “I look back on this experience with deep remorse.”

Mr. Epshteyn (pronounced EP-stine) has not commented on the case, and his lawyer has not returned requests for comment. Ms. Ellis’s lawyer has also not returned requests for comment.