Why not have on-air real-time fact checking during presidential debates? Perhaps the worst aspect of political debates is candidates’ self-flattering phony claims: Viewers have no way of judging whether the claims are true or false. So appoint a fact checker! The obvious candidate is PolitiFact, sponsored by the St. Petersburg Times, which is devoted to verifying or denying the assertions of politicians. In 2009, PolitiFact won a Pulitzer Prize for its work. Here is PolitiFact’s fact-check of last week’s Republican debate.

Suppose that while candidates were speaking, a neutral third party such as PolitiFact checked all factual claims and reported its findings the moment the debate concluded: or even live, in a crawl as candidates were speaking. Candidates would be furious about this, because then they’d have to tell the truth, or at least stop making preposterous claims. There would be obvious public benefit in presidential debate fact checking. What are we waiting for?