Well, actually he already has. She is so "nasty". Not to mention she picked on poor justice Kavenaugh.Look at Biden's share of female voters. An effective trust exercise with this large and growing bloc of support is likely to pay political dividends. Before I'm "But Hillary'd" here we have to come to terms that Harris and Clinton are very far apart in terms of public perception which is why Trump can't think of any good way to attack her.
Especially ironic since Trump has a nasty nickname for nearly everyone who opposes him.