Donald trumps positive test for coronavirus has added a new layer of uncertainty to what was already the most turbulent and unpredictable us election for decades. to have a president in isolation, even if not incapacitated, has implications for security and the functioning of us government at the best of times let alone a month before polling day in a bitterly fought election. yet despite mr trumps attempts to cast doubt on them, americas institutions and its constitution remain robust enough provided all other players in the political system stick to the rules to deal with whatever consequences his infection may bring. this news organisation, meanwhile, joins all those wishing the president and the first lady a full and speedy recovery.

Whether mr trumps experience of coronavirus proves mild or more serious he was said on friday to be well his positive status will have immediate implications. in a country with a higher degree of scepticism than many others towards the pandemic and preventive measures such as mask-wearing, fuelled in part by the presidents downplaying of the threat, it will bring home the reality and severity of the pandemic.

It will change, too, the nature of the campaign, though not the central issues at stake between the two candidates. for the foreseeable future, mr trump will no longer be able to hold the large rallies that have been the mainstay of his re-election bid. it will be difficult for him to mock the caution shown by his rival, joe biden, whom he has accused of hiding in his basement. it will also be trickier for mr trump to shift the focus from his own handling of the outbreak, in a country which has recorded the worlds highest number of coronavirus deaths to date, and on to ground where he feels more comfortable. in recent weeks, the president has attempted to divert attention to the strength of the pre-pandemic economy, his nominationof amy coney barrett to the supreme court, and recent violence in us cities. his own condition will now put the pandemic front and centre.

Yet the falls in equity markets and rising indicators of volatility after mr trumps test emphasise the extent of unease now surrounding the poll. jpmorgan has noted that the 2020 election has seen a historically wide margin of event risk priced across asset classes by options markets. investors fear not just a lengthy dispute over the results but the potential for a broader stand-off, or even violence, after the presidents refusals to commit to a peaceful transfer of power should he lose the election.

Mr trump, and his supporters too, have repeatedly sought to cast doubt on the validity of the election, suggesting the use of millions of mail-in ballots, to avoid having to vote in person during the pandemic, opens up the potential for fraud. what is vital is not to allow the presidents coronavirus status however it may develop to be used as a further means to discredit the election. fear-mongering, rumour and innuendo should not be allowed to derail due process.

The two parties have rules in place, should this ever become necessary, to choose replacement candidates. the twenty-fifth amendment, adopted in the 1960s, sets out procedures if a president is incapacitated, and has been invoked several times since. congress has powers to alter the election date by changing relevant statutes. with the pandemic raging, and the latest jobs numbers suggesting the us recovery is stalling, republicans as well as democrats should commit to sticking to the letter of the rules.

Mr trumps infection may yet prove mild and brief. even if it does not, the system if respected is still robust enough to accommodatesuch a shock.