Harris has open-border policies that lead to “massive problems” in a range of other areas, like “parents who can't afford health care, schools that are overwhelmed; it's got to stop, and it will when Donald Trump is president.”

Vance and Walz are facing each other in their first and possibly last vice presidential debate, hosted by CBS in New York on Oct. 1.

Both are relatively unknown to the broader American public. Walz was a U.S. House member before becoming governor of Minnesota. Vance is in his first term as a senator from Ohio.