There are two kinds of negative political frames: issue and character. Character frames can be divided into contrast (experience, judgment, etc.) and integrity (dishonesty, corruption, etc.).

The worst kind of political attack is an unsubstantiated attack on an opponent’s integrity, impugning their honesty and trustworthiness without a shred of evidence. There’s really not much worse you can say about another candidate than that they are corrupt.

And that’s exactly what Bernie has been doing for all of 2016. His aides, surrogates and supporters have been doing it as well, even more directly and aggressively. Tad Devine went so far as to question Hillary’s capacity to appoint a Supreme Court Justice to replace Scalia.

And Bernie did it again tonight, implying that contributions to Hillary somehow corrupt her. It’s the Wall Street dog whistle, a deplorable negative frame that Hillary rightfully swatted down during a recent debate:

I debated then Senator Obama numerous times, and he was the recipient of the largest number of Wall Street donations of anybody running on the Democratic side ever. Now, when it mattered, he stood up and took on Wall Street. He pushed through, and he passed the Dodd-Frank regulation, the toughest regulations since the 1930’s. So, let’s not in anyway imply here that either President Obama or myself, would in anyway not take on any vested interested, whether it’s Wall Street, or drug companies, or insurance companies, or frankly, the gun lobby to stand up to do what’s best for the American people.

Bernie is piggybacking on 30 years of rightwing smears and trying his level best to accomplish what Karl Rove and his ilk have failed to do: destroy Hillary’s public image and make her out to be dishonest and untrustworthy.

Thankfully, voters see through the false narratives and are carrying Hillary to victory. And respected public figures from Morgan Freeman to Dolores Huerta to John Lewis to Russell Simmons are rejecting the smear tactics.

That doesn’t make Bernie’s attack any less reckless, especially when we’re facing the likes of Trump and Cruz. It’s long past time for him to focus on issues and let go of the character destruction.

(Nam Y. Huh/AP Photo)