The Supreme Court. Climate change. ISIS. The economy. Education. Putin. North Korea. Refugees. Poverty. Inequality. Injustice. Intolerance.

The list of challenges for the next president goes on and on.

Democrats have two candidates. Assume for the sake of argument that they each have a 50% chance of winning the nomination. And assume the Democratic nominee will face someone like Donald Trump or Ted Cruz in the general election.

With so much on the line, why is one of them waging an all-out war on the other’s integrity?

Why on earth would Bernie Sanders run a campaign premised on the destruction of Hillary’s public image?

As we’ve written: Hillary let Bernie off the hook in the last debate. She could have asked him a simple question: Does he believe President Obama is corrupt because of financial industry contributions? It’s a yes or no question that is central to the 2016 race.

Does Bernie think President Obama is compromised by Wall Street contributions? If so, he should have the courage to say it. If not, he shouldn’t imply that a female candidate would be influenced by donations or speaking fees. There’s a word for that.

The endless drumbeat that Hillary is dishonest is now driven directly from the top of Bernie’s campaign. The candidate doesn’t say it in so many words, but the inference is crystal clear. It is an “artful smear” where any mention of the “establishment” or Wall Street is a Pavlovian trigger designed to impugn Hillary’s character. The Wall Street Dog Whistle.

No matter how lofty and inspiring Bernie’s message, no matter how much he motivates younger voters, it is deeply unjust – and frankly, reckless – to run a campaign premised on the destruction of Hillary’s character through false innuendo. And make no mistake, Bernie’s campaign message and the behavior of his supporters have become less about something and more against someone. His path to victory runs right through Hillary’s integrity. It’s a deeply regrettable turn of events in an election where Bernie had initially vowed to stay positive and issue-driven.

And no, Hillary isn’t reciprocating. Her criticisms are about drawing a contrast with Bernie’s unrealistic proposals, to bring a dose of reality to the dreams he’s selling to eager young voters.

There is no Bernie revolution. Democratic turnout is down. There is nothing but the harsh truth that America could veer sharply right in November and we need our candidates intact, not mangled and battered.

Lest any Bernie supporter question this premise, they should first explain this:

In a story in Sunday’s New York Times, Bernie Sanders’ top adviser, Tad Devine, took a very nasty shot at Hillary Clinton: “She cannot be trusted to appoint someone to the Supreme Court who will take the issue of campaign finance seriously,” he said.

Democrats just don’t do that to other Democrats.

Bernie is now presiding over a campaign and a contingent of supporters who are willing to treat Hillary more disdainfully than Rove and the GOP. Crossing that line is crossing to the dark side of politics.

Surfing a wave of hate for one of the most admired and respected women on the planet is beneath him and beneath any true Democrat.