Julian Castro: I wasn't taking a shot at Biden's age

“I wasn’t taking a shot at his age, I was taking a shot at the fact that he had just said the words “Buy-in.” You would have to buy in,” Castro said.

“It’s not an attack on Vice President Biden. It’s not something about personality. It’s about the health care policy. That was my focus,” he added.

Castro’s comments have been widely panned as a “low blow” and while it did earn the former House and Urban Planning Secretary under the Obama administration a great deal of attention, it is not clear that this is the sort of attention he would want.