Earlier this month, the world’s most battle-scarred cable news network did something extraordinary in this year of vaporous political contrails. While Donald Trump was delivering one of his easily debunked lies, CNN fact-checked him — in near real time at the bottom of the screen.

“Trump: I never said Japan should have nukes (he did).” Thus read the chyron that shook the television world — maybe.

I no more expect CNN to set Wolf Blitzer’s beard on fire than to instantly call out the Mount Everest of liars. Trump lies about big things (there is no drought in California) and small things (his hair spray could not affect the ozone layer because it’s sealed within Trump Tower). He lies about himself, and the fake self he invented to talk about himself. He’s been shown to lie more than 70 times in a single event.

Given the scale of Trump’s mendacity and the stakes for the free world, it’s time that we go into the fall debates with a new rule — an instant fact-check on statements made by the candidates onstage. The Presidential Debate Commission should do what any first-grader with Google access can do, and call out lies before the words hit the floor.