You’ve been hearing more than normal about post-in ballots this US election campaign.
Millions of them have already been cast, and they are likely to play a key role in the outcome of Wednesday’s election.
But what happens to them once they’re posted, where are they now, what’s being done to keep them safe, and when will they be counted?
How many people have voted before election day?
While people can hand in their postal ballots at designated drop boxes, most are lodged through the US Postal Service (USPS).
Each US state has its own rules and timelines on when early voting occurs.
Some started in September. Some didn’t start until mid-October, or even closer to election day on November 3.
The USPS itself has become the focus of a controversy after President Donald Trump said postal votes led to increased voter fraud, and Democrats accused Mr Trump of gutting the service to suppress voter turnout.
Why the US Postal Service is under the spotlight
The United States Postal Service is at the centre of a fierce political storm, with both sides of politics weighing in on how its operation may threaten the integrity of the November election.
Since then, US District Judge Emmet Sullivan has ordered the USPS to release daily reports on mail deliveries, participate in daily court conferences and take other steps to ensure timely delivery of ballots.
On Thursday last week, the USPS said it had delivered 122 million blank and completed ballots.
More than 97 million Americans have already cast ballots in the election, according to a tally by the US Elections Project at the University of Florida.
This includes about a record 62 million mail-in ballots.
There were just over 29 million votes still outstanding, it said.
What happens to mail-in ballots once voters fill them out?
Mr Trump’s claims of increased fraud linked to postal voting are not backed up by research.
Most of the time ballots are mailed to processing stations where they’re verified before being counted.
Many states made it easier to request a mail ballot this year over concerns about crowded polling places on election day during a pandemic.
But there have been reports of small numbers of undelivered ballots.
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For example, USPS investigators said on Saturday they found six completed ballots and 42 blank ballots among piles of undelivered mail in a Florida post office.
The investigation was launched after Florida politician Kionne McGhee tweeted a video taken by a postal worker of the piles of undelivered mail.
“The fight is no longer at the ballot box but at the post box,” Mr McGhee, a Democrat, tweeted.
On Monday, a Federal judge ordered the USPS to take “extraordinary measures” to deliver ballots in time to be counted in the key battlegrounds of Wisconsin and Michigan, including using a priority mail service.
The judge said on-time delivery of ballots sent by voters was too slow in these states.
What happens to ballots once they’re posted?
Once the ballots are received they are processed, recorded and verified by the local election administration.
But the way this is done can vary slightly between states.
Most states check the voter’s signature and address on ballot envelopes against county records and voter registration forms.
Those that don’t match are rejected.
Once they are verified, ballots are either opened and prepared for counting, opened and counted, or kept closed until the election day, depending on the state.
Signed envelopes with addresses are also removed by hand to ensure anonymity.
Some ballots may not be counted due to reasons unrelated to the eligibility of the voter — such as arriving late, missing a signature or a technical problem.
There are currently a number of lawsuits underway to reduce or prevent ballot rejections, as this issue could be pivotal in key states.
However, many states have in place processes for officials to contact voters if there are discrepancies on their ballot papers.
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When will they all be counted?
Ballots are kept locked in a dedicated location, such as on the premises of the election office or in another Government building, until they are ready for the count.
Counting takes place with an audience including volunteers, party representatives and the media, to verify the fairness of the process.
Just as there are different timelines for early voting across the 50 US states, there are different timelines for how the votes are counted.
Some states allow the “processing” of mail-in ballots — the often time-consuming flattening and opening of envelopes, verifying signatures and sorting ballots into the correct piles for tabulation — to begin as many as three weeks before election day.
Some only allow it to begin on election day itself, which can lead to a chaotic and lengthy count.
That’s the process in several key swing states.
Democrats fear this will delay the count of mail-in ballots, expected to heavily favour Democrats, and give Mr Trump a misleading early lead that he could seize on to declare the election over.
US media outlet Axios reported this week that Mr Trump told close advisors he intended to declare victory on election day if it looked like he was ahead.
He denied the report, but said: “I think it’s terrible that we can’t know the results of an election the night of the election.”
What impact could they have on the final outcome?
The higher-than-average number of early votes and mail ballots means we could be waiting for days for an official outcome.
The US Elections Project at the University of Florida says about 45 per cent of early voters are registered Democrats, compared to 30 per cent who are Republicans.
That could lead to what some call a “red mirage”, where it looks like the Republicans are out in front until all the early votes are counted.
As unofficial tallies are updated and votes are counted, some experts have identified a “blue shift”, whereby the Democrats make major gains as official results are tallied.
This is likely to be even more pronounced in 2020, given the much larger numbers of postal and early votes.
Because of concerns about submission deadlines, USPS backlogs and the potential for drawn-out legal challenges, Democrats are now pressing their backers who have yet to return ballots to head to the polls in person.