With the Clintons, mistrust always pays.

A couple of weeks ago, Hillary was yukking it up with Jimmy Kimmel over the absurdity of rumors that she was hiding something about her health. Look, she can open a pickle jar! That feels so long ago now that her campaign has admitted that she was indeed hiding something about her health — a pneumonia diagnosis late last week.

Some of the diagnoses from afar of Hillary’s purported illnesses have been elaborate fantasies, and she might have really been fit as a fiddle when she opened the famous pickle jar. But through her secretive handling of her pneumonia, she has, once again, shown how it never pays to trust a Clinton.

Bill and Hillary have a way of treating the credibility of their allies as a disposable commodity, in this case including the credibility of a protective media.

The press had worked itself into a lather in recent weeks about the illegitimacy of inquiries into Hillary’s health. They were repaid by Clinton leaving reporters behind without notice at the Sept. 11 memorial; nearly collapsing when she was out of their view (the incident was captured on video by a bystander); giving them a wave and a misleading “feeling great” outside of Chelsea Clinton’s apartment, where she had gone to recover; and leaving them behind yet again to go to her home in Chappaqua and see a doctor.

Her campaign initially said Hillary “overheated” (on a gorgeous and mild morning in New York City). Can happen to anyone, right? Well, yes — and especially someone walking around with a case of pneumonia.

Bill and Hillary have attracted more than their share of kooky conspiracy theories, but they also have vindicated some of the darkest suspicions of their most passionate detractors.

Only a hater would have believed that Bill Clinton, embroiled in a sexual-harassment case, would have an affair with a White House intern. Only a hardened cynic would think that Hillary, serving as secretary of state and assured to make a front-running campaign for the Democratic presidential nomination, with every incentive to keep her nose clean, would mingle private and public business to aid her family’s already incredibly well-funded foundation. Only a kook would wonder about her occasional coughing fits.

And we know how all of that turned out. It is a cliche in the press to say that Hillary hurts herself by not being more transparent. But cover-ups have their advantages. If things had bounced differently, Bill might have been able to get away with denying his affair with Monica Lewinsky; we might never have learned of Hillary’s private server; and Hillary’s pneumonia diagnosis might have been kept under wraps, too.

Surely, the public had a right to know. Millions of people get pneumonia every year, and often it is easily treatable, yet the condition is serious enough that Hillary’s doctor told her to scale back her campaign schedule. The public interest in disclosure took a back seat to Hillary’s interest in not giving any more fodder to critics questioning her vigor.

Clinton has now been caught being dishonest about an area where public skepticism is most justified. Politicians lying about or concealing health problems is a common feature of every political system the world over, democratic or totalitarian, East or West. Hillary would do well to adopt an uncharacteristic policy of complete transparency about her health records and perform the rest of the way without a disruption more serious than a stray sneeze.

Even if she does, the handling of her pneumonia is a preview of how a second Clinton White House would operate. If she’s elected president, inevitably, some outlandish allegation will arise. The Clintons and their defenders will dismiss it as a hateful fantasy, before — when all other options are exhausted — admitting it’s actually true.

This is the Clinton pattern over a couple of decades of stoking, and validating, their critics’ distrust.

Rich Lowry can be reached via e-mail: comments.lowry@nationalreview.com.