Why don't we know who has won the US presidential election?

Democratic presidential challenger Joe Biden is just six Electoral College votes shy of the 270 he needs to win a majority and therefore the race for the White House, ousting Donald Trump from the Oval Office after just one term.

Although Mr Biden failed to secure the landslide triumph the polls had been predicting in advance of Tuesday’s ballot — with red states supposedly in contention like Florida, Texas and Ohio all falling to Mr Trump — the Democrat scored a string of important victories to put him in the driving seat, with Arizona, Wisconsin, Minnesota and Michigan all projected to turn blue.

But the country remains embroiled in uncertainty after a chaotic election night failed to produce a clear winner, with neither candidate winning enough states to hit the magic number.

We still do not know who has won on Thursday morning because four crucial battleground states have yet to announce their results: Nevada, Georgia, North Carolina and Pennsylvania.

In others like Alaska, Arizona, Michigan and Wisconsin, ballot counts are still being finalised, meaning they could potentially still be in play, further muddying the picture.

Arizona, for instance, has been called for the Democrat by both the AP and conservative broadcaster Fox News, but Mr Biden’s lead is understood to have been diminished somewhat as the count continues.

The reason for the delay is, of course, the coronavirus pandemic, which has forced many key states to extend their ballot-processing after receiving an influx of mail-in votes, with millions of people preferring not to take part in person to limit their risk of exposure to Covid-19 by queuing in long lines.

Nevada suspended its count in the early hours of Wednesday morning but is expected to deliver its total later on Thursday.

If that goes Mr Biden’s way, the state’s six Electoral College votes would take him from his current 264 to 270 and we would have a winner, a 46th president and an end to the Trump era.

North Carolina and Pennsylvania’s verdicts could come in even later though, with the states winning court rulings in the face of Republican challenges giving them until 12 November to chalk up their final answers.

If Mr Biden does not get a win in Nevada or in Georgia in the meantime, the country could hypothetically still be in limbo in a week’s time.

A legal challenge from Mr Trump could further delay matters.

The president prematurely declared victory for himself in a speech at the White House in the early hours of Wednesday morning before the counting had even been concluded while alleging that unspecified “fraud” had been rampant in the process (without providing evidence), calling on the US Supreme Court to step in.

Both campaigns are fundraising for potential court battles in key states, with Mr Trump already demanding a recount in Wisconsin with Mr Biden ahead by less than one per cent.