Hillary Clinton's pneumonia diagnosis will send rumours about her health into overdrive

The US presidential race is, quite simply and by some distance, the world's most gruelling political contest.

It requires endless travelling on almost no sleep, fundraising for years on end, constant speech-making, and a level of scrutiny that would drive the rest of us insane.

Now imagine you are doing it as the first female candidate in US history; that there are tenacious political opponents who have spent a lifetime trying to undermine and defeat you; that you are 69 years old next month, and that your health is the subject of conspiracy theories and wild rumour.

And with just nine weeks to go, you are diagnosed with pneumonia.

Hillary Clinton has reportedly had to cancel a planned campaign trip to California because of her pneumonia diagnosis. Credit: Reuters

Welcome to the world of Hillary Clinton, where every misfortune is a cause of celebration for your political enemies.

Right-wing blogs, conservative talk-radio and maverick websites have been spreading rumours for years, claiming that Mrs Clinton is physically, mentally and emotionally unfit for the demands of the Oval Office.

It is implicitly sexist and often outrageously conspiratorial in nature. Some claim Hillary is close to death; that a secret service agent travels with her at all times with a syringe filled with a mysterious medicine; and that she never recovered from a concussion she suffered three years ago.

The truth is likely to be more pedestrian. Mrs Clinton is exhausted and has been hit by allergies and now by pneumonia. Her doctor insists she is in generally fine health and is recovering well.

But, without a shadow of a doubt, that won't satisfy those who wish to see her defeated in November. They will interpret the video of her stumbling into the van yesterday as "proof" that she hasn't the stamina to be president and commander-in-chief.

Now the rumours about Hillary's health will be flying faster than ever before, and the speculation that once existed only on the fringes of the Internet has entered the mainstream.

In the brutal, binary game that is presidential politics, that will be judged as ominous news for Hillary and encouraging news for Team Trump.