The Princeton group has a simple message: That the machines that Americans use at the polls are less secure than the iPhones they use to navigate their way there. They’ve seen the skeletons of code inside electronic voting’s digital closet, and they’ve mastered the equipment’s vulnerabilities perhaps better than anyone (a contention the voting machine companies contest, of course). They insist the elections could be vulnerable at myriad strike points, among them the software that aggregates the precinct vote totals, and the voter registration rolls that are increasingly digitized. But the threat, the cyber experts say, starts with the machines that tally the votes and crucially keep a record of them—or, in some cases, don’t.

Since their peak around 2007, voting districts have begun to rely less on the digital voting machines—a step in the right direction, as states bolt for the door on what the programmers describe as a bungled, $4 billion experiment. Instead, rushing to install paper backups, sell off the machines and replace them with optical scanners—in some cases, ban them permanently for posterity. But the big picture, like everything in this insular world, is complicated. As the number of machines dwindle—occasioned by aging equipment, vintage-era software that now lacks tech support, years without new study by the computer scientists, and a public sense that the risk has passed—the opportunities for interference may temporarily spike. Hundreds of digital-only precincts still remain, a significant portion of them in swing states that will decided the presidency in November. And, as the Princeton group warns, they become less secure with each passing year.