She is the porn star at the center of the criminal trial of Donald J. Trump whose name has been uttered by witness after witness. But up to now, Stormy Daniels has existed only in the imagination of the jurors who will decide Mr. Trump’s fate — a main character who is off to the side of the stage.

That may be about to change. Ms. Daniels could take the stand to testify against Mr. Trump as early as this week. It would be their first face-to-face confrontation stemming from the revelation six years ago of the $130,000 hush-money agreement on the eve of the 2016 presidential election to buy her silence about a sexual encounter she says they had.

The dramatic decision to call Ms. Daniels to the stand would carry both possible benefits and definite risks for prosecutors for the Manhattan district attorney, Alvin L. Bragg. Her presence would let Mr. Trump’s defense lawyers attack Ms. Daniels as an extortionist and question her credibility.

Still, her testimony would allow jurors to see and hear from the person at the core of the case. Ms. Daniels could also offer context about the environment in which she sold her story of their 2006 encounter, which Mr. Trump denies. She was shopping the story as Mr. Trump’s campaign was reeling in 2016 from the disclosure of a recording on the set of Access Hollywood in which he bragged of groping women.

Michael Bachner, a New York City defense lawyer not involved in the case, said that if prosecutors did not call Ms. Daniels to testify, “it would just be a glaring hole” that the defense would question.