Coronavirus has the potential to stop in-person campaigning in the 2020 US election. Here's why Facebook, Google and Twitter could face an unprecedented stress-test in November.

• The spread of coronavirus might mean the US has an unprecedented presidential election with almost no traditional in-person campaigning.
• In the absence of a conventional political campaign, digital platforms like Facebook, Google, and Twitter will be more important than ever in the democratic process.
• Over the last few years, these companies have struggled with various political issues - including the spread of misinformation, whether to fact-check politicians, and how to handle rule-breaking by world leaders.
• If COVID-19 continues through the summer and campaign rallies and events are cancelled, those issues will take on ever-greater importance - and the tech companies will face new levels of scrutiny.
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This week, in the face of the mounting coronavirus outbreak, Joe Biden cancelled a series of fundraisers and rallies in Florida and Illinois less than a week before the Democratic primaries in those states.

The abrupt actions suggest at a possibility that was until recently unthinkable: This year, the United States might be forced to hold a presidential election with almost no traditional in-person campaigning of any kind.

COVID-19, the disease caused by the novel coronavirus, has sickened more than 125,000 and killed more than 4,600. The stock market tanked on Thursday in the face of a response from President Trump that was perceived as inadequate and an increasing realization that the crisis may continue to grow for months.

It's by no means clear how long this will last, but if the more pessimistic predictions prove accurate, public health measures may yet force the curtailment of most or all traditional door-to-door political campaigning. And into this void will step digital platforms like Facebook, Google, YouTube, and Twitter - companies that have struggled for years with how to police political content.

In California, San Francisco has banned gatherings of more than 1,000 people. Schools in Seattle, Washington and surrounding areas have closed. The entire NBA has been suspended. Italy, which is further advanced in its outbreak than the US, is in a state of nationwide lockdown, closing bars, restaurants, and nearly all shops.

If this disruption continues over the next few months, that could mean no campaign rallies. No town halls. No meet-and-greets at Iowa diners. No candidates eating local delicacies on a stick at a county fair. No door-knocking. No slogan-emblazoned tour buses. No rowdy crowds at televised debates. No appearances at mid-tier sports games. No cross-country campaign planes. No handshakes, autographs, and endless selfies.

Campaigning would effectively be reduced to TV ads, appearances on cable news, mailed flyers and promotional materials, billboard advertising, and, of course, digital. Picture locked-down voters, barely able to leave their homes, being fed through their social feeds an unending stream of posts, ads, videos, and pop-ups, alternately promoting or tearing down the candidates.

Social networks like Twitter and Facebook, search engine Google, and its sister video sharing service YouTube were always going to play an extraordinary role in the 2020 election. Their precise micro-targeting ad capabilities have led to political campaigns throwing hundreds of millions of dollars at them in advertising in recent years (and also spending countless hours making and sharing non-ad content).

But the once-lauded companies have struggled under the pressure, with intense scrutiny of their platforms on issues ranging from whether to fact-check political advertising to alleged rule-breaking by world leaders, transparency over ad spending, voter suppression campaigns, and the unchecked spread of malicious misinformation.

The companies say they've made significant progress since 2016, when Russians were able to proliferate across the social networks, spreading blatant hoaxes and inflaming political tensions. But ongoing debate around the classification of political material, the adequacy of fact-checking programs, approvals of misleading political advertising, and other issues indicates there may still be work to be done.

In the absence of more conventional campaigning, these tech companies will wield more power over American politics than ever before. It's vital that they get it right this time.

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