Russian hackers would not be able to change the outcome of the United States presidential election, the nation’s most senior intelligence and law enforcement officials have assured Congress and the White House in recent weeks. But disrupting it, they acknowledge, would be far easier — causing doubts in battleground states, prompting challenges to results and creating enough chaos to make Florida’s hanging chads seem like a quaint problem from the analog age. By some measures, in fact, the disruption has already begun. And meddling around the edges of an election could sow doubts about the legitimacy of the results — especially in a year in which the Republican nominee, Donald J. Trump, has told his supporters that the only way he will lose is if the election is “rigged,” and while campaign officials for his Democratic opponent, Hillary Clinton, have held a series of meetings about preparing for the possibility that the vote will be hacked. The White House has declined to name Russia publicly as the chief suspect in a series of recent hacks, and has worded its public warnings carefully. The greatest danger, Lisa O. Monaco, President Obama’s domestic security adviser, said on Wednesday, is from attempts to cause “concern or confusion” about the voting system.
… A recent attempt to steal voter registration rolls in Arizona by what the F.B.I. told state officials were Russian hackers, and a successful theft of voter information in Illinois, raised the question of whether the lists of registered voters at polling stations could be manipulated. One fear is that newly registered voters could be struck from the rolls. They could still cast provisional ballots, but the result would be long lines and delays. Another is that nonregistered voters, foreigners or felons who have been barred from voting might be able to enter the voting booth, leading to challenges.
Voting machines are not supposed to be connected to the internet (though there are some exceptions), providing some additional measure of protection. But results are reported online, and one fear that federal cyberexperts have discussed is that a sophisticated “man in the middle” attack could allow hackers to take over internet systems used to report unofficial results on election night. Such a breach might not alter the official ballot count, but it could sow deep mistrust about the numbers that are broadcast.
… Until recently, said Pamela Smith, the president of Verified Voting, a San Diego-based nonprofit that advocates improvements to voting equipment and systems, a manipulated election seemed more like a theoretical problem than a real possibility. But the hacking of the Democratic National Committee’s internal emails and of voter registration databases in Arizona and Illinois has focused minds. “It’s a reality check for the whole country,” Ms. Smith said.