PBS moderator: Is Bernie Sanders 'thwarting history' by challenging Hillary?

A moderator at a Democratic primary debate Thursday evening asked Sen. Bernie Sanders, I-Vt., whether he had any misgivings about running against Hillary Clinton given that she could very well be the first female president of the United States.

“Senator,” said PBS Gwen Ifill, “do you worry at all that you will be the instrument of thwarting history, as Senator Clinton keeps claiming, that she may be the first woman president?”