Update: As this story was being published, Green party candidate Jill Stein announced that she is asking for donations to fund a recount of her own in Michigan, Pennsylvania, and Wisconsin, which are the states key to Hillary Clinton’s surprising loss. Stein says she must raise $2.5 million by Friday 4 pm central time to proceed.

In an election besieged by hacks into the emails of leading Democrat officials, and voter registration systems in Illinois and Arizona, a leading expert on election counting says Hillary Clinton should call for a recount in key states that used machine ballot counters.

J. Alex Halderman, a computer scientist at the University of Michigan, details in a Medium post that states that count ballots with machines rather than paper ballots are liable to be hacked with malware. That could change the numbers just enough for one candidate to overtake the other: “If my Ph.D. students and I were criminals, I’m sure we could pull it off,” he writes. In states like Wisconsin and Pennsylvania, where Donald Trump’s margin of victory was around 1%, that could plausibly be enough to tip the balance.

Halderman acknowledges it’s an unlikely scenario, but argues that the currently accepted explanation (that polls were wrong more or less across the board) isn’t “overwhelmingly more likely” than the polling stations being hacked.

Polling guru Nate Silver poured cold water on suggestions that the result could be overturned, despite that fact that Clinton does have better results in larger Wisconsin counties that used paper ballots. In a series of tweets, he argued that once you factor in race and education (which he says were “key factors” in determining 2016 voter shifts), the “the effect COMPLETELY DISAPPEARS.”

For Halderman, however, the question of overturning the election isn’t the only reason to have a recount. He says even a recount that found everything was fine would ”help allay doubt and give voters justified confidence that the results are accurate,” and “set a precedent for routinely examining paper ballots, which will provide an important deterrent against cyberattacks on future elections.”