National Guard troops are on standby and businesses have been boarded up in Washington DC in case unrest breaks out in the aftermath of the presidential election.
As millions of Americans prepared to cast their votes on Tuesday, there were widespread concerns the US could see a repeat of the violence that followed Trump’s 2020 election defeat, when rioters stormed the US Capitol.
The concerns have been fuelled by baseless claims made by Donald Trump at rallies in recent days.
The former president, and Republican presidential hopeful, has claimed without proof that cheating is already underway in the election.
At rally after rally, he has told supporters the only way he can lose is if Democrats cheat, and he has repeatedly refused to say whether he will accept the results regardless of the outcome.
Ms Harris' Democrats, meanwhile, were on Tuesday preparing for the possibility that Trump could try to prematurely claim victory before all votes are counted, as he did in 2020.
Shops and businesses near the US Capitol in Washington DC have been boarded up with plywood ahead of Election Day, while anxious voters said they worried about what could happen, especially if Trump loses.
Sherry Gay-Dagnogo, a 57-year-old Harris supporter in Detroit, said she is concerned about what Trump's incendiary rhetoric could provoke. "It's like he's igniting a base of violence in advance," she said. "It's scary."
Lillian Hall, a 68-year-old former teacher from Hendersonville, North Carolina, and a Trump supporter, said she was scared there would be rioting if Harris loses.
“I think there'll be anger like we've not seen yet if Trump wins,” she said.
A Reuters/Ipsos poll conducted last month found widespread worries that the US could see a repeat of the unrest that followed Trump's 2020 election defeat, when the then-president's false claim that his loss was the result of fraud prompted hundreds of followers to storm the US Capitol.
Some 74% of registered voters who responded to the survey said they were concerned extremists would commit acts of violence if they were unhappy with the election results.
More than half of the 50 states have indicated they will be willing to send National Guard troops to Washington if requested following the election and in the run-up to the inauguration, Guard officials said.
The District of Columbia has not made any formal requests for Guard troops, but officials across the government have been preparing for the possibility the US Capitol could again be rocked by violence.
About 25,000 Guard troops from around the country flooded into Washington in the days after January 6, 2021, when thousands of Trump supporters stormed the Capitol in an effort to prevent Congress from certifying President Joe Biden's win.
Guard members have historically provided support for presidential inaugurations, but the 2021 event involved an enormous response, with Guard forces arriving by the busload as the riot forced lawmakers to flee.
The troops, along with local and federal law enforcement, locked down the city for the inauguration, securing the Capitol, monuments, Metro entrances and the perimeter of the central part of the city.
Colonel Jean Paul Laurenceau, chief of future operations for the National Guard Bureau, said on Monday it is not yet clear how many Guard troops will be needed or requested this year.
"We're here to support DC with sustainment, lodging, transportation - anything they need to prepare for this mission," he said.
Other officials have said it also will depend on intelligence reports assessing the potential threats to the city and the transition of power.
In 2021, a few states declined to send troops, also worried about violence within their own borders and capitals.
Defence officials said on Monday that 10 states have activated state Guard members to assist with the election - primarily with cybersecurity missions.
The District of Columbia and nine other states had by Monday put Guard troops on standby, ready to deploy if needed. Those states are Colorado, Florida, Hawaii, Nevada, Oregon, Pennsylvania, Tennessee, Texas and West Virginia.
