On Tuesday, the progressive legal war on Exxon will head to trial in a case most notable for … how badly it has fizzled.

It started back in 2016, with “a move many are hailing as a ‘turning point,’ ” as EcoWatch proclaimed: 20 state attorneys general launching an “unprecedented, multi-state effort” to probe and prosecute the oil giant.

The central charge — seemingly bolstered by Pulitzer-nominated journalists: Exxon had for decades hidden “key climate science.”

Actually, only a few AGs — including then-New York Attorney General Eric Schneiderman, who spearheaded the effort — led any investigations. And today, only two cases exist: the one from the New York AG’s office, and another from the Massachussets AG — which is on hold and likely dead.

Yet the big press conference, which featured climate-change icon Al Gore, fueled the #exxonKnew movement — and accomplished a key goal: drawing headlines.

“Exxon Mobil Climate Change Inquiry in New York Gains Allies,” reported The New York Times. “Attorneys General Will Investigate Energy Firms For Climate Deception,” announced BuzzFeed.

The claim: Exxon had long known that consuming oil would cause global warming but hid the facts. In fact, the company for decades published findings closely matching mainstream science. No one has ever produced any evidence of a coverup.

Which is why Schneiderman (before the revelation of horrifying personal conduct ended his career) was forced to find a different rationale: Big Oil, he said, might be “overstating” its assets by “trillions,” by failing to account for potential future regulations that restrict fossil fuels.

Oops: The company had warned about the risks of new rules; that’s why a Securities and Exchange Commission probe cleared it of those charges.

And the case that now-AG Letitia James takes to trial Tuesday is a huge comedown from even that claim, charging that Exxon fraudulently used two sets of books to state the risks. The company says it merely releases different estimates for different purposes, with full disclosure.

The charge is not only a far cry from the original #ExxonKnew allegations, it’s also almost certain to fail. Putting the best face on this fact, climate-change warrior Andrew Revkin tweeted Wednesday: “Some lawsuits are fought for the win, some are fought for the documents. The NYS #exxonknew suit is far more likely to be the latter.”

In fact, the entire thing has been a shameless exercise in prosecutorial abuse, from the outrageous harassment of nonprofits whose research the climate-crisis crew dislikes to the ethically dubious private funding of staff in the New York AG’s Office.

Radicals might think anything is justified in the effort to destroy the fossil-fuel industry, but prosecutors betray their public trust when they bend the law to push a private ideological agenda.

If you have a real case, you don’t have to make up fake ones.