Dripping with disdain, the 140-character [Twitter] asides got under Trump’s skin (admittedly, not the hardest of feats). He accused her of “tweeting violently” and bestowed on the senator one of his trademark churlish nicknames. “Goofy Elizabeth Warren,” he replied in tweets of his own.

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.”