Philadelphia – Pennsylvania's largest city – has stopped reporting the results of mail-in ballots for the night in a move that has sparked fury among Americans anxiously awaiting the election result.
The decision to stop reporting new results until 9am tomorrow morning (US time) is significant because it means the results we do have so far for the state could be tilted in Donald Trump's favour.
A national spokesperson for the GOP has declared that the halt in reporting is evidence of fraud.
The decision caused widespread confusion this afternoon after it was initially believed the city was abandoning counting altogether for the night - however, a livestream of the vote count paints a different picture.
So far, only around 76,000 of the city's 350,000 mail-in ballots have been counted, and with Biden fans more likely to vote by mail, it means we won't be seeing an accurate representation of the state's results until counting resumes.
And in a further blow, election officials have said a final result might not be known until Friday.
It's especially important because out of all the so-called battleground states, Pennsylvania has long been seen as the most crucial of all.
It is considered to be the most likely "tipping point" state, meaning if the election comes down to a single state, Pennsylvania is probably going to be the one – which is why the decision to halt counting has caused so much panic.
What this means for the election's outcome
There may be 50 states in America, but when the votes are counted, just a handful of them – Pennsylvania included – decide who wins the presidential election.
In this election, 15 states fall into the category of a "swing state" or "battleground state" – meaning they could conceivably be won by either Donald Trump or Joe Biden.
As for the rest, we already know who will win them: Trump stands no chance whatsoever in Democratic Party strongholds like New York and California, for example, while he's likely unbeatable in heavily Republican territory, like Alabama or Oklahoma.
In 2016, Trump broke the Democrats' six-election winning streak in Pennsylvania – worth 20 electoral votes, blowing up the idea that it had shifted from purple to solidly blue.
It was pretty close though, with a margin of just 0.71 per cent.