Democratic presidential candidate Bernie Sanders clashed Monday with a reporter who asked if it was sexist for him to run against the potential first female president of the United States.

"What do you say to women that say you staying in the race is sexist and getting in the way of what could be the first female president?" a female reporter asked Sanders at a press conference in San Francisco.

"Is that a serious question?" Sanders responded immediately.

The reporter affirmed that it was a serious question.

Sanders fumbled for a moment and then attempted to clarify her question.

"Your question implies that any woman, that any person, any woman who is running for president is by definition the best candidate," Sanders said. "So any woman who runs — to say that it is sexist that any — so if Hillary Clinton runs for president is your point, that it is sexist for any man to oppose her?"

"My point is if she has more delegates than you ..." the reporter responded.

"Then that is another point. That is not — I don't think it is sexist," Sanders responded. "I think that the issue is, first of all, our focus right now is running and winning right here in California. And the second point that I have made is that it is absolutely imperative that we defeat Donald Trump as president of the United States."

The race between Sanders and Democratic front-runner Hillary Clinton in California has been close, and some polls even indicate the Vermont senator has a narrow lead. The California primary will be held on Tuesday and Clinton is just shy of 26 delegates needed to secure the Democratic nomination.