Former Vice President Mike Pence never said Donald J. Trump’s name.

In 21 minutes on the Iowa State Fair soap box on Thursday, Mr. Pence referred to Mr. Trump as “my former running mate” and “the former president” but made no reference to anything that happened during what he usually calls “the Trump-Pence administration.”

Mr. Pence avoided these references even when a voter in the crowd — a supporter of President Biden — accused him of having committed “treason” on Jan. 6 in a question, eliciting boos from an otherwise respectful crowd.

“I know you might have a different impression about what my duties and responsibilities were on Jan. 6, and I’m happy to talk to you about it,” Mr. Pence said.

What he didn’t know was that the man who had shouted the question at him was a retired postal inspector who had traveled from Colorado for a bit of political performance art.

“I want Pence to have to explain himself at every event,” the Democratic heckler, David Stelzer, said afterward. “He spent two years quiet and allowed this thing to fester, this disease, this cancer, to fester, and that’s why we’re in the case were in.”

Mr. Stelzer added: “He’s not going to win the nomination and he’s not going to go down in the history books as a courageous leader.”

Mr. Pence, who regularly gets similar questions from fellow Republicans, took the question in stride.

“There’s almost no idea more un-American than the notion that any one person could pick the American president,” Mr. Pence said. “People deserve to know that on that day, the former president asked me to choose between him and the Constitution. I chose the Constitution and I always will.”