Technology will be critical to tabulating votes in a contested election, though recounts and delayed counts in a few swing states are unlikely to tip the all-important Electoral College vote.
Critics say some election technology, particularly the automated or direct-recording electronic (DRE) voting machines used by many jurisdictions, is flawed, outdated and liable to manipulation when the machines do not produce a paper audit trail.
Even DREs connected to printers are problematic, according to election expert Philip Stark, professor of statistics and associate dean of mathematical and physical sciences at University of California, Berkeley.
"Touchscreen voting machines are a terrible solution for the vast majority of voters," Stark said. "They introduce software between the voter and the paper record, which has the effect of making the paper record hackable.
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"The paper record becomes a record of what the machine did, rather than what the voter did," Stark added.
Automated signature verification
Another tech factor that could come into play in a close finish between President Donald Trump and Democratic candidate Joe Biden is the performance of optical signature verification systems, with an expected unprecedented volume of mail-in votes triggered by COVID-19 pandemic safety concerns.
Signature verification tools can speed the process of "curing" or matching signatures on mail-in ballots to signatures on voter registration records, but these technologies produce both false negatives and positives. Also, many local election systems don't have digital signature matching.
Signature matching systems use a camera to capture a voter's signature from the ballot return envelope as it's sorted. The system then compares the signature with the reference image from the voter registration database.
Meanwhile, signature matching protocols vary as much among states, counties, cities and towns as do voting procedures.
A common complication is that signatures change over time and have become even more variable in the digital era, in which people rarely need to write their signatures manually.
Technology has advanced
But signature-matching technology and methods have improved significantly over the years, said Ted Allen, an associate professor of integrated systems engineering at The Ohio State University. He has studied the use of systems engineering methods to run efficient and accurate elections.
Election officials can now more easily compare and verify contested ballots on the basis of signature variations, Allen said.
"If there are contested signature cures from the mail-in ballots, there's a good chance they will be processed more accurately," he said.
Also, more voting districts are moving away from DREs in an effort to create a better paper trail, Allen said.
"There's reason to be optimistic that systems have generally improved," he said.
A lesson from the 2000 election
Ironically, the famously contested 2000 presidential election between former President George W. Bush and Al Gore hinged largely on paper ballots in Florida, notably those with the so-called hanging chads. Hanging chads were partially punched voting cards with slivers of hanging paper. Election officials had to rule on whether they constituted a valid vote.
So, while it's a welcome development that punch card voting systems are largely extinct, at least the punch cards offered some kind of usable paper audit trail, Stark said.
Philip StarkProfessor, University of California, Berkeley
Nearly all election districts now use fill-in-the-oval scanned ballots, which produce a paper receipt. DREs also came into favor after the 2000 election but have been plagued with well-documented problems.
Unlike in the tech world, where digital records are considered sufficient in many cases, truly fair elections should include paper evidentiary trails because votes can't be refunded or re-done if something goes wrong, Stark maintained.
"At least with hanging chads, there was a paper record," he said.
Also, expected slowdowns at the U.S. Postal Service caused by budget cutbacks and an expected unprecedented volume of mail-in ballots could cause vote-counting delays both in uncontested states and in states where a recount is required.
Recounts mostly 'won't matter'
Amid concern about the reliability of election technology and Trump's unsubstantiated claims about widespread mail-in voting fraud, it's improbable that ballot-counting accuracy will be a major nationwide problem.
That's because the U.S. voting system is an amalgam of thousands of local and state voting districts, with a dizzying variety of voting, collecting and tabulating procedures, machines and training methods.
Each state decides its own winner and loser in a national election. The winner is awarded all that state's votes in the Electoral College, regardless of how close the winning margin is.
So, while many anticipate a close election -- no matter what the polls say at the moment – few expect a tight enough vote in most states to warrant a recount, even if the numbers in the Electoral College, which requires 270 votes to win, are close.
Only in a handful of crucial swing states with large numbers of Electoral College votes – such as Arizona, Florida and Pennsylvania – will the popular vote be near enough to force a recount or significantly delayed count, said Rob Gray, a Republican political consultant in Boston.
Most states will almost certainly go comfortably Democratic or Republican, as per the blue state-red state paradigm, most political observers agree.
Mail-in voting seen as secure, accurate
Gray ran the campaign of former Massachusetts governor Paul Cellucci, consulted for former Massachusetts governor Mitt Romney and was a recount manager for Bush in north Florida in 2000.
He disagrees with Trump's assertions about mail-in voting fraud and said the chances of irregularities in voting and counting votes are slim.
"Trump's rhetoric on mail-in ballots is distasteful to me as a Republican because it reduces confidence in our electoral system, and it's exaggerated because if it's a problem at all, it's not some type of nationwide problem," he said.
Mail-in voting is "an efficient and safe way to collect and count votes," he added.
Meanwhile, Gray said he finds DREs "troubling," not because they favor Democrats or Republicans, but because they leave election officials without an indisputable way to double-check vote counts.