The more important reaction came not from Trump, however, but from Hillary Clinton‘s campaign. Multiple sources close to the former secretary of state say that her aides took note of the senator’s ability to rile the real estate tycoon. And they recognize the value of such dart throwing from, say, someone filling out a presidential ticket.

One close Clinton confidant said that she and her aides were “thrilled to see Warren get under his skin.” Another senior Clinton adviser, who is advocating internally for Warren as a vice presidential pick, said the senator has “very influential people in the campaign pushing for her.”

A longtime Clinton veteran said the campaign definitely noticed Warren’s attacks. “You want a running mate who can take the fight to the other side with relish,” the veteran said. “Geography does not matter, but attitude and talent and energy and bringing excitement to the campaign, Senator Warren does all that.”