At a hearing last month on the possible hacking of voting machines, Louisiana Secretary of State Tom Schedler said he was more worried about something else. The real threat on Election Day, said Schedler, is violence at the polls.

Poll workers across the country are on high alert after the recent firebombing of a Republican Party headquarters in North Carolina and reports that two armed men lingered for hours outside a Democratic campaign office in Virginia. Some feel that Donald Trump's claim that the election is rigged, and his suggestion that supporters and their friends to go to polling places to "watch," are rhetorical time bombs.

"You know, it's unfortunate that we have to do this, but we want to be overly prepared," said Amber McReynolds, the director of elections for the city and county of Denver. "We have added in an active shooter training into our election judge training."

McReynolds says she wants poll workers to be prepared to handle any scenario in a calm and responsive way. They also have a central hotline they can use to report any problems, and which allows her office to track what's going on throughout the city on Election Day.

"And if we need to mobilize the police department or another emergency response team, we can do that pretty easily," she said.

Matt Masterson is on the U.S. Election Assistance Commission, a federal agency that works with state and local election offices. He says almost every jurisdiction has a detailed plan for voting place emergencies. Many of those plans were beefed up after the Sept. 11 terrorist attacks, which occurred on a primary election day in New York City. With the tone of the current election, Masterson thinks those plans are now getting extra attention.

"My guess is many election officials, they've gone back, rechecked them, made sure that their poll workers are trained on exactly how to handle any kind of escalation of conversation in the polling places," said Masterson. "They know exactly who to call and when to call when something happens."

He says one way to avoid Election Day confrontations is to make sure that everyone — including poll workers, candidates and outside monitors — knows the rules in advance. For example, can voters carry guns into polling stations? In many places, that's strictly prohibited, but not in open-carry states.

Schedler said this week that it's a difficult balance for election officials — making voters feel safe, but also welcome.

"I'll have people ask, 'Well are you going to have a sheriff's deputy at every precinct?' No. I just, you know, the sight of an individual there, standing there with a gun, to me is just something that you shouldn't have to experience typically as a voter."

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