"This election the environment is unlike any before," South Carolina Election Commission spokesman Chris Whitmire said.
Some states are trying to coordinate with local law enforcement to tighten security without making a heavy-handed - and potentially illegal - show of force. And some schools that double as polling places have canceled classes on Election Day for fear of agitated voters and demonstrators in school hallways.
Over the weekend, a firebombing heavily damaged a local Republican Party office in North Carolina. No injuries were reported. And after a bomb threat at the Arizona GOP headquarters on Monday, the state party said it will probably hire security guards.
As Trump's poll numbers have dropped amid accusations from multiple women that he groped them without consent, the Republican nominee has warned that the election is about to be stolen from him on Nov. 8 by backers of Democrat Hillary Clinton.
Trump has called on people to act as "election observers" in certain areas of the country to help prevent fraud - a move that has stirred fears of voter intimidation and confrontations at the polls.
