Donald J. Trump has criticized Carly Fiorina’s looks, saying of his only female Republican rival: “Look at that face! Would anybody vote for that?” He has said that listening to Mrs. Fiorina’s voice gives him a “massive headache.” He has mocked her business career, and has gleefully declared how “viciously” she was fired by Hewlett-Packard.

On Wednesday, Mr. Trump will share a stage with Mrs. Fiorina for the first time, in the second Republican presidential debate.

Political strategists warn male candidates to use caution when debating against a female rival. But almost never before in American presidential politics has a candidate who has drawn charges of sexism and bullying been forced to personally confront the female recipient of his insults on live television. And with Mrs. Fiorina bragging that she is getting under Mr. Trump’s skin, their showdown is emerging as one of the most intriguing subplots of the second debate.

Read the article “Fiorina/Trump Showdown Expected at Republican Debate” on nytimes.com.