In general, you shouldn’t pay much attention to polls at this point, especially with Republicans unifying around Donald Trump while Bernie Sanders hasn’t conceded the inevitable. Still, I was struck by several recent polls showing Mr. Trump favored over Hillary Clinton on the question of who can best manage the economy.

This is pretty remarkable given the incoherence and wild irresponsibility of Mr. Trump’s policy pronouncements. Granted, most voters probably don’t know anything about that, in part thanks to substance-free news coverage. But if voters don’t know anything about Mr. Trump’s policies, why their favorable impression of his economic management skills?

The answer, I suspect, is that voters see Mr. Trump as a hugely successful businessman, and they believe that business success translates into economic expertise. They are, however, probably wrong about the first, and definitely wrong about the second: Even genuinely brilliant businesspeople are often clueless about economic policy.

An aside: In part this is surely a partisan thing. Over the years, polls have generally, although not universally, shown Republicans trusted over Democrats to manage the economy, even though the economy has consistently performed better under Democratic presidents. But Republicans are much better at promoting legends — for example, by constantly hyping economic and jobs growth under Ronald Reagan, even though the Reagan record was easily surpassed under Bill Clinton.