(CNN) - The US intelligence community, election officials and social media companies will be on high alert as Americans go to the polls Tuesday to vote in this year's midterm elections, guarding against potential electronic threats to the integrity of the results.
They'll be watching not just for signs of continuing interference from Russia, as intelligence officials believe happened in the 2016 presidential election, but for a host of potential pitfalls -- from rogue social media posts to real-world power outages.
An outright hack is the No. 1 concern of intelligence officials, politicians and voters.
The US intelligence community says there is no evidence any votes were changed by hackers in 2016 and that they haven't seen the same level of activity from the Russians this election cycle as they did in 2016.
America's election infrastructure is vast and varied. Different states, even different counties within states, use different systems. The lack of a centralized national system could make it more difficult for hackers to achieve a widespread attack.
But no system is perfect, and technology experts have long warned about the vulnerability of election systems to hackers. That hasn't improved as voting systems have aged: In August a group at a hacking conference in Las Vegas exposed vulnerabilities in some of America's voting machines.
Here are three other things that could go wrong:
The appearance of a hack
Much easier than hacking a voting system would be to claim a hack had occurred and then watch those claims go viral on social media.
The perception of a hack could have the same effect on the integrity of election results as an actual hack.
Fourteen states have no paper records or only partial paper record of votes, making audits more difficult if hacking claims emerge after an election.
Some people reported during early voting in Texas that machines were flipping their votes. Democrats voting "straight ticket" reported their votes for Senate candidate Rep. Beto O'Rourke changing to Sen. Ted Cruz. State election officials -- as well as the manufacturer of the voting machines -- say it was human error, with voters failing to use the system properly.
Another potential weak spot: Voter rolls.
Over the weekend, Georgia's Republican secretary of state Brian Kemp -- who is himself running for the governorship -- claimed that the Democratic Party had tried to hack the state's voter database, after Georgia Democrats passed along information regarding security concerns from a voter to a private cybersecurity firm, which in turn shared the issue with Kemp's office.
Democrats, including gubernatorial nominee Stacey Abrams, called the allegations partisan and baseless.
State officials said Monday they had opened a criminal investigation, creating an appearance of wrongdoing that could cast doubt on Tuesday's results.
Misleading posts go viral
While there are plenty of things that can, and will, go wrong on Election Day, social media can make routine disruptions seem suspicious, seeding confusion and doubt.
On Election Day 2016, a video purporting to show a voting machine preventing someone from voting for Donald Trump in Pennsylvania went viral, picking up tens of thousands of retweets and prompting widespread claims of vote rigging.
But, as CNN later reported, the voter didn't use the machine properly -- and it turned out he was able to vote for Trump after all.
Last week, NBC News reported that at least some of the attention the Pennsylvania video received on Election Day was the result of Russian-government-linked trolls that were apparently amplifying it to sow confusion.
The worst fear is voters falling for bad information and changing their plans because of it.
In 2016, a Russian troll group ran an online disinformation effort attempting to convince Hillary Clinton supporters that they didn't need to go to a polling place to vote, and instead could vote online or by text.
A similar tactic was used by an unknown group on the morning of last November's gubernatorial election in Virginia -- and the tweets went undetected by Twitter for hours, CNN found. There is no indication the tweets impacted the election.
The lights go out
Hackers needn't attack voting machines to disrupt an election. Power outages affecting traffic lights or attacks on phone systems can create havoc and force officials to focus on the issues as they arise, diverting police and other government resources and potentially dissuading voters from going to the polls.
Ever since it emerged that Russia had targeted America's power grid, experts have explored what impact targeted power outages, which would affect everything from voting machines to traffic lights, could have on elections.
Adding to concerns: US officials found evidence that Russia was behind a power outage that left tens of thousands of Ukrainians in the dark in 2015.
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