When you have no idea what you are saying, those mistakes sometimes pop out.

Via The Hill:

Chelsea Clinton made an attention-grabbing verbal slip Wednesday when she accidentally referred to Democratic presidential candidate Bernie Sanders as “President Sanders” while speaking with her mother’s supporters in Minnesota.

Speaking at a campaign event in Eden Prairie, the former first daughter was attempting to paint Hillary Clinton as the superior choice for Democratic voters, but inadvertently handed the White House to her mother’s rival.
“I hope not ‘President’ Sanders!’ ” Clinton said after quickly correcting herself, to laugher from the audience.