On election day, voters in Pennsylvania will be touching the lighted buttons on electronic vote counters that were once seen as the solution to messy paper ballots.
But in the event of a disputed election, this battleground state — one of the few that relies almost entirely on computerized voting, with no paper backup — could end up creating a far bigger mess.
Stored in a locked warehouse near downtown Harrisburg, the 1980s-era voting machines used by Dauphin County look like discarded washing machines lined up in rows. When unfolded and powered up, the gray metal boxes become the familiar voting booth, complete with a curtain for privacy.
Much may rest on the reliability and security of these aging machines after an unprecedentedly combative presidential campaign that is ending with Donald Trump warning repeatedly of a "rigged election" and his refusal at Wednesday's debate to commit to accepting the results on Nov. 8.
The GOP nominee has specifically targeted Pennsylvania as a state where the election may be "stolen," despite no evidence to back up such a claim and several polls showing Democratic rival Hillary Clinton well ahead of him here.
"The only way we can lose," he told a recent rally in Altoona, "is if cheating goes on."
Trump's talk has put extra pressure on election officials to make sure the voting is free and fair, and the tally is accurate and reliable. And there is little reason to doubt it will be.
But computer experts says the old electronic voting machines have a hidden flaw that worries them in the event of a very close election. The machines do not produce a paper ballot or receipt, leaving nothing to be recounted if the election outcome were in doubt, such as in 2000, when the nation awaited anxiously for Florida to reexamine those hanging chads.
"The nightmare scenario would be if Pennsylvania decides the election and it is very close. You would have no paper records to do a recount," said Lawrence Norden, deputy director of the Brennan Center for Justice's Democracy Program, co-author last year of a report on the risk posed by old voting machines.
About three-fourths of the nation's voters will be marking paper ballots, most of which will be counted electronically by an optical scanner, said Pamela Smith, president of Verified Voting, a nonpartisan group that has advocated for paper ballots that can be counted electronically and recounted by hand as a way to ensure trust in a close election.
California and most of the battleground states — Ohio, Florida, North Carolina and Virginia among them — have switched to voting systems with a paper trail.
By contrast, Delaware, Georgia, Louisiana, New Jersey and South Carolina entrust their votes entirely to electronic touch screens.
Pennsylvania is among those states that rely almost entirely on computerized voting, according to Verified Voting.
"Pennsylvania is using technology from the '80s made by the companies that don't exist anymore. In computer years, that's a very long time ago," Smith said.
Pennsylvania election officials say they are well aware of the challenges.
Gerald Feaser Jr., elections director for Dauphin County, agrees the older voting machines "are not sophisticated," but he said that may be virtue. "They can't be hacked," he said, because they were never connected to the Internet.
"Could the Russians hack our website on election night? Yes," he said. But nearly 500 voting machines across the county would be untouched and their vote tallies unaffected, he said.
County election directors like Feaser nevertheless have a duty to make sure each of their voting machines is tested, working properly and correctly programmed for its precinct. Dauphin County has 162 polling precincts around Harrisburg and in the surrounding rural areas. Pennsylvania does not allow early voting, so the election begins at 7 a.m. on Nov. 8.
Marian Schneider, a voting rights lawyer who was appointed last year as Pennsylvania's deputy secretary for elections, said she was well aware of the problem with electronic machines. Still, the "risk of tampering is very low," she said.
But Andrew Appel, a Princeton professor of computer science, said that given a screwdriver and seven minutes with an electronic machine, he could "install a vote-stealing program" that would be hard to detect and shift a percentage of the votes.
In states like Pennsylvania, these voting machines "are delivered to polling places several days before the election — to elementary schools, churches and firehouses," he said. That creates the risk of tampering. "This is not just one glitch in one manufacturer's machine. It's the very nature of computers," he told a House subcommittee last month.
Feaser said state and local officials take precautions to ensure machines are kept secure and can't be tampered with.
But Appel nevertheless recommends that the nation "eliminate the use of paperless touchscreen voting machines" after this year's election.
Other computer experts acknowledge the problem but do not see it as significant or ominous.
"It's true they have a potential vulnerability. You can put a bug in the software and switch some votes. But you would be talking about one machine and a few hundred votes," said Michael Shamos, professor at Carnegie Mellon University in Pittsburgh. "It's not a systemic problem. These machines are not connected, and they are tested regularly. I have voted for years on these machines and do not have a security concern."
In Allegheny County, which includes Pittsburgh and more than 1,300 voting precincts, election officials do random tests of voting machines on election day to check for tampering or irregularities.
"We randomly select 20 machines and pull them out of service," said Mark Wolosik, the county election director. "We have an independent lab test them. We have been doing this since 2008 and haven't found any problems," he said.
Election officials and most party leaders — Republicans and Democrats — reject Trump's talk of the election being "stolen" or "rigged."
In Pennsylvania, polling places have a judge and two inspectors — representing the two major parties — to watch over the voting. And each side can have three designated "poll watchers" monitor them. They may challenge a voter who does not live in the area or is not who he says he is.
"There are a lot of eyes watching at the polls. They're Republicans and Democrats," said Ralph Teti, a Philadelphia lawyer and a Democrat who for many years represented the city's election board. "They know the people in the neighborhood. The idea that you can bus people in from outside the area is just absurd."
Michael Korns, the Republican chairman in Westmoreland County in western Pennsylvania, said he sees "no reason to be concerned" about the fairness of the vote counting. "I don't believe there is any danger in the election being 'rigged'. That's just what people say when you lose," he said.
For their part, the election officials say they would welcome newer voting machines, but the cost is the problem. "The counties can't afford it. And these machines have worked well for us," Feaser said.
In Pittsburgh, Wolosik said election officials are treating this election just like every other. "We hope everything goes well on election day," he said. "And the election is not close."
On Twitter: DavidGSavage