If we can learn anything from the latest triple-bank-shot of a conspiracy theory coursing through the alt-reality media — this one involving the unsolved murder of a Democratic National Committee staff member named Seth Rich — it’s this: Fake news dies hard.

God knows people have tried. In the last few months, journalists, academics, technology experts, civic-minded foundations and well-intentioned politicos have devoted decades of collective brain hours to an all-hands effort to stanch the conspiracy theories and outright falsehoods roiling our democracy.

Facebook and Google have worked up new computer formulas and dispatched dedicated teams of humans to push the corrosive stuff off their platforms or, at the very least, to let readers know when something doesn’t look right. Ad makers are pulling their advertising from sites that run false items. And educators are working up “news literacy” programs to teach students how to tell the difference between real, corroborated journalism and naked lies dressed in the colors of veracity.

But as the Seth Rich story shows, we’re going to need a bigger algorithm.

In case you haven’t been following it, the Seth Rich conspiracy holds that before his death (or, in this version of events, assassination) in July Mr. Rich had been involved in the leaking of Clinton campaign emails to WikiLeaks, which the United States intelligence community has attributed to Russian-sponsored hackers.