In the autumn of 1955, Dwight D. Eisenhower began feeling poorly on a Colorado golf course, the result, he reckoned, of eating too many onions.

It was a heart attack. The world didn't find out until days later, at which point the stock markets tanked.

So yes, you might say the health of the president of the United States is germane to the job. It doesn't explain the near-hysteria over Hillary Clinton's failure to disclose a bout with "walking pneumonia" – a jumped-up chest cold.

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The episode barely rates in the pantheon of presidential ailments, but then no one – from Ike, who later had a stroke while in office, to Ronald Reagan, a symptomatic Alzheimer's patient in his second term, or back to Teddy Roosevelt, who went blind in one eye after a boxing mishap and told no one for months – had to contend with opponents' surrogates yapping on 24-hour cable news and propaganda mills like Breitbart News and the Drudge Report churning out months' worth of conspiracy theories about their health.

Perhaps Mrs. Clinton feared her illness would feed into a panic. But had she revealed her minor, treatable malady earlier, would there have been any less of a stink?

Republican nominee Donald Trump is no more transparent than she is about medical or tax records, yet opacity seems to be a particular liability for Mrs. Clinton; the default presumption is that she must be hiding something.

Part of it is self-inflicted; she is a serial obfuscator and stretcher of truths – whether it's about a private e-mail server or the nexus between the Clinton Foundation and her office. As flaws go, she is a galaxy away from Mr. Trump, an intemperate vulgarian who appeals to the grimmest recesses of the American id.

He is also a policy ignoramus who is vowing, loudly, to run roughshod over illegal immigrants, Muslims, trade and foreign affairs – when he isn't flip-flopping, that is.

A thoroughly poisoned environment gives everyone a seedy hue.

The Democratic nominee is an imperfect candidate, but Mrs. Clinton's shortcomings cannot be compared to Mr. Trump's; they are not of the same genus. One is running a viable candidacy for high office. The other is a bigoted boor.