And that word is: millionaire.
You probably can't rattle Donald Trump with jabs at his racism, sexism, psychological volatility, foreign policy bellicosity, domestic policy ignorance, or general piggish behavior. He doesn't care about that shit. What he does care about is not being seen as a loser.
Now Trump clearly wears his "billionaire" status like a codpiece, but nobody really knows if he actually has a billion dollars. So there's no reason for Hillary Clinton to give him the benefit of the doubt. When Lester Holt asks her about her tax policy, she should begin her answer with the following:
First of all, Lester, the American people need to know that my opponent's tax policies would line the pockets of millionaires such as himself and leave the middle class holding the bag...
This would be accompanied by an obvious glance at Mark Cuban, who, unlike Trump, is an undisputed billionaire, as well as being a much younger and better-looking reality television star. And Hillary should refer to Trump as a “millionaire” whenever she can.
He won't be able to ignore it, believe me.