DUBUQUE, Iowa – A journalist for the Spanish-language network Univision who asked Donald J. Trump about immigration was mocked by the candidate, then escorted out of a news conference here on Tuesday evening.

Jorge Ramos, an anchor for Univision news shows based in Miami, stood and began asking a question just as Mr. Trump recognized another reporter. “Excuse me, sit down. You weren’t called,” Mr. Trump told him. “Sit down. Sit down.”

Mr. Ramos asked Mr. Trump about his call to deport 11 million undocumented immigrants in the country and build a wall the length of the Mexican border.

“You haven’t been called, go back to Univision,” Mr. Trump said.

As security officers approached Mr. Ramos, a Mexican-American, he said: “I am a reporter. Don’t touch me. I have a right to ask the question.”

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He was escorted from the room by a security guard.Credit Charlie Neibergall/Associated Press

Mr. Trump was silent as Mr. Ramos, an Emmy-winning journalist who was on the cover of Time magazine’s World’s Most Influential People issue, was removed from the room. Several other journalists asked Mr. Trump why he refused to take questions from Mr. Ramos. The billionaire real estate investor, who is leading in Republican polls for the presidential nomination, said it was because he had asked a question without being called on.

In an interview on CNN on Monday, Mr. Ramos accused Mr. Trump of “spreading hate” with his calls for mass deportations of undocumented families and repealing birthright citizenship granted by the Constitution.

“This is personal,” Mr. Ramos told CNN. “When he’s talking about immigrants, he’s talking about me.”

About 15 minutes after his ejection on Tuesday, Mr. Ramos returned, and he and Mr. Trump engaged in a long back-and-forth about Mr. Trump’s immigrationproposals, frequently talking past each other.

Mr. Ramos said that building a border wall would be futile because 40 percent of undocumented immigrants arrive by plane. “I don’t believe it,” Mr. Trump said.

“How are you going to deport 11 million?” Mr. Ramos asked.

“Very humanely,” Mr. Trump said.

At one point, Mr. Trump pressed Mr. Ramos to tell him how much Mr. Trump was suing Univision for, after the network dropped coverage of Mr. Trump’s Miss USA and Miss Universe pageants because of his remarks about Mexican immigrants. Mr. Trump answered his own question: $500 million.

Mr. Trump insisted he would win the Latino vote. Mr. Ramos cited a poll saying that 75 percent of Latinos hold an unfavorable opinion of him.