Bernie’s ill-fated decision to go hard negative on Hillary is an object lesson in poorly conceived political strategy. His advisers should have spent more time studying her history of making attackers regret their actions.

We’ve predicted for months that Bernie’s insistence on impugning Hillary’s character would damage his brand, not hers:

A funny thing happens to people who think they can take down Hillary Clinton by assailing her character: they end up with their own reputations in tatters.

For most of 2015, Bernie focused on issues that matter. He promised not to run a negative campaign. He brought crucial topics into the national spotlight. It was enlightening and inspiring, even for Hillary supporters.

As 2016 dawned, something happened. Bernie and his strategists determined that their only path to the nomination ran directly through Hillary’s integrity. And they pursued that mission on all fronts, using aides and surrogates to paint Hillary as dishonest and corrupt.

Tad Devine, Bernie’s top aide, took this cheap shot at Hillary:

“She cannot be trusted to appoint someone to the Supreme Court who will take the issue of campaign finance seriously.”

Hillary reacted to these low blows with grace and dignity:

You know, Senator Sanders has said he wants to run a positive campaign. I’ve tried to keep my disagreements over issues, as it should be. But time and time again, by innuendo, by insinuation, there is this attack that he is putting forth, which really comes down to — you know, anybody who ever took donations or speaking fees from any interest group has to be bought. And I just absolutely reject that, Senator. And I really don’t think these kinds of attacks by insinuation are worthy of you. And enough is enough. If you’ve got something to say, say it directly. But you will not find that I ever changed a view or a vote because of any donation that I ever received.

But Hillary’s admonition did nothing to stop the personal attacks. It was a terrible mistake for Bernie, but he doubled down on the attack strategy — and his surrogates and supporters followed suit.

Now, Bernie is reaping what he sowed. The long dormant vetting process has begun, with the media and pundits finally recognizing that he has been unfairly assailing Hillary’s character.

What’s more, a can of worms has been opened with respect to Bernie’s record. Questions are cropping up about his own contributions, his investments (a fracking company?) and his tax returns.

On the latter, the hashtag #ReleaseTheReturns is gaining rapid traction on Twitter. We included it in the title of this story only to illustrate the blow-back Bernie is receiving for attacking Hillary and we do not intend our use to be interpreted as a call for him to release his returns.

If anything, we expect no surprises in his returns. We have also called on Bernie and his supporters to stop the ridiculous “release the transcripts” attack on Hillary, which is nothing more than a way to cast aspersions on her character.

Bernie is learning the hard way that throwing mud at Hillary only sullies the person who threw it. He would be wise to reconsider his decision, though it’s likely too late.

(AP Photo/Nam Y. Huh)