“John Bolton is at the nexus of Russia’s interference in our democracy and the NRA’s reckless agenda”: The sentence is so bonkers, so pristine in its conspiratorial insanity that it should one day grace a Museum of Natural History exhibit on early-21st-century US politics.

Yet it wasn’t from an anonymous troll, or some Hollywood figure with tons of followers but little common sense. It was tweeted by National Security Action — an outfit run by former top Obama officials.

Described by the Washington Post as a “political strike force,” this NSA is a coterie of veterans from the Obama White House and Hillary Clinton’s campaign, acting as a shadow government to weaponize foreign-policy disputes. It’s a fever-swamp-in-exile.

And it exemplifies everything that’s wrong with top Democrats’ partisan madness in the Age of Trump.

The co-chairs are Ben Rhodes and Jake Sullivan. Rhodes, you’ll recall, was the reckless novice Barack Obama made a top adviser who proceeded to create what he called an “echo chamber” of lies, distortions and spin about the Iran nuclear deal for pro-Obama reporters and think-tankers to regurgitate.

Sullivan’s presence atop a conspiracist machine is more troubling. Unlike Rhodes, he’s knowledgeable, experienced and inclined to public service. Had Clinton won the 2016 election, Sullivan would’ve been the front-runner for national security adviser — the post to which Bolton has just been named.

What’s up with this Bolton/Russia stuff, anyway? It’s all based on the fact that Bolton was asked in 2013 by the then-NRA president to record a pro-gun rights statement for a Russian organization. For that, Sullivan’s group accuses Bolton of being “at the nexus of Russia’s interference in our democracy”? Is Jake Sullivan really comfortable with this?

Or, for that matter, is former Obama chief of staff Denis McDonough, who serves on the National Security Action advisory council? What about Tom Donilon, who held Bolton’s job under Obama? Susan Rice and Samantha Power, who, like Bolton, are previous US ambassadors to the United Nations? They too serve on the advisory council.

If you want to understand what’s behind this rabid partisanship, two other members of the council make more sense: Joe Cirincione and Wendy Sherman. Cirincione is a key member of the “echo chamber.” He’s president of the Ploughshares Fund, a leftist group that, in the years leading up to the nuke deal, funded media (including National Public Radio) and nuclear “experts” to whom it distributed talking points on the nuke deal intended to sell the Obama administration’s party line.

Sherman was the chief negotiator of the Iran deal.

And Bolton hates the nuke deal and wants President Trump to scrap it. His opposition stems mostly from the fact that it’s a disastrous mess that legitimized Iran’s program, knifed US allies — and unchained Tehran’s terror squads with an infusion of cash and a willingness by Obama to look the other way as they bloodied up the Middle East.

It’s a national embarrassment. Rhodes, Cirincione and Sherman couldn’t be prouder of it.

And that’s really what’s going on. The smear of Bolton by Team Obama is the echo chamber reverberating to save its legacy project.

In the New York Times this week, Sherman excoriated Bolton as a warmonger for wanting to tear up the deal: “The march to military conflict will be hard to stop, especially with Mr. Bolton leading the National Security Council.” With the deal in place, Iran won’t build nukes, because . . . the mullahs pinky-swore: “Iran has committed to never obtaining a nuclear weapon.”

As absurd as this sounds, it’s a key talking point: If you don’t like the deal, you want war, and anyway Iran promised.

On Tuesday, Ernest Moniz, the Obama energy secretary also involved in nuke-deal talks, wrote in the Boston Globe: “The core of the Iran agreement is an explicit commitment from Iran that it will never seek, develop or acquire nuclear weapons.”

Chiming in to Politico was Sullivan, warning, “It is very difficult to overestimate the potential danger that John Bolton could put us in.”

These former Obama advisers think they’re protecting one legacy, but really they’re creating a separate one. In their willingness to cross any line to slime public officials who differ, they are encouraging the public to reinterpret their time in office not as a high-minded search for truth and security but as a series of partisan exercises soaked in the politics of personal destruction.

Twitter: @SethAMandel